The authors of Genesis claimed a hammered out bracelet divided two sources of water, the water below Heaven became our Seas and the water above still exists beyond the Heaven (snowline).
The Latin translation introduced the concept of a hammered bracelet. That was an error. The words were written with the concept of a "stretching out". Not a "hammering out". When a bracelet is hammered it is stretched. Hammering does not give it a firmness. The metal already has firmness. If anything hammering it too thin, may weaken it, not strengthen it. The concept was not making a firm place, but stretching out what was already in place. So the authors of Genesis did not compare what happened to a hammered bracelet. That was not even thought of until the Romans added their own interpretation, and used the Greek word for firm, instead of the Hebrew word that does mean hammer or spread. It was used in describing how to make a bowl by hammering it out into the shape that is needed. But it has nothing to do with making a firm or fixed area in space.
Saying that the Earth came from the "snow line" is not separating the waters, and that would be wrong, as the earth is not the center of the solar system. Nor would moving the earth closer to the sun be the same concept as creating an area around the earth to keep the waters separated. This water cannot be separated too far away from the earth, or it would make no sense in even mentioning it. It would just disperse through out space. If it held it's properties that far out, then the original body would have to take up volumes of space in order for it to still be recognized as a body of water that encompassed all the planets and the sun that were inside of the "snow line". Then you would have to explain how all that water was able to come back through all of that space to provide the water for the Flood which was also included in the narrative. The only thing that is plausible, is that it only encircled the earth, and even modern science claims that is not possible. It was an extra thickness to the atmosphere, and it is a fact that there are still huge chunks of ice that fall from that area of space. It does not claim that there was X amount of water, that would have not been feasible. It just says that there was an area of water surrounding the earth.
Some hypothesize that the earth did not have seasons, until a heavy bombardment event (IMO at the time of the flood) caused this area of water to break apart, and also gave the earth it's current angle of rotation to give us seasons. There were no ice caps before the Flood and no seasons. In reading the translated cuneiform tablets from the attacks of Assurbanipal even in the 7th century BC, there were huge tracks of forest found across the Arabian peninsula. Now it is just a desert. Once they were all cut down from the human intrusion, the area had no ability to re-grow them, but at one time the conditions were right for them to flourish with or without human intervention.
If a large body did go through the water surrounding the earth, it would have had enough impact to change the earth, and even the moon, that humans had known. While at the same time not as drastic if there had not been a layer of water around the earth. It would have happened on the other side of the land mass that humans lived on, and would have broken up both the fountains of the deep, and the fountains above the earth. The Complete Jewish version reads, "all the fountains of the great deep were broken up, and the windows of the sky were opened". A large body would open the sky like a window, and break up the crust in such a way to release the water under the crust. This collision would also add mass to the earth and a smaller earth could have accounted for the discrepancies in ages that are found in the records of the pre-flood humans. It is interesting that the rain did not flood the earth, until forty days later. The ark did not float until the fortieth day, after the rain stopped. An impact would have only lasted for at least a day. It was not a dry impact, but a liquid one. While it threw off debris that reached the moon, it only rained for 40 days, as the only effect of those in the account. The Inuit stated that the earth was lifted up, before the flood, and then the waters rushed in. For Noah after the rain stopped there was a huge tsunami that must have come in and lifted the ark up and over the mountains where it was built.
The sons of God had children with human women, these were the Nefilim and their lifespans diminished over time.
The sons of God were still flesh and bone humans. They were just not the seed of Adam. The whole concept was that Adam was created separate, and we today all descended from him. That is not entirely true. One claim says that Adam was created without knowledge and then gained it. The other claim is that Adam was the only human created. They both are wrong. Adam was created along with all the other humans in the same fashion as them, and they all were sons of God. The "sin" of Adam was disobeying God, not gaining a knowledge that caused him to be just as smart as God. All the sons of God knew right from wrong, because Cain feared that they would kill him, for murdering his brother. The "sin" of Adam only changed his descendants to no longer be the sons of God. Seth was not a son of God, but a son of Adam. It was the daughters of Adam's descendants who were impregnated by the unchanged sons of God who were all the other humans alive before the Flood.
You claim that the "120 years" was the countdown to the Flood, but that is not logical. God saw all humans as mortal flesh (sons of God, and daughters of men) and limited them to only live 120 years. That is why they claimed that Moses was 120 but still had years of life left in him. There was nothing wrong with him that would cause his life to be relegated by the normal life expectancy. In fact him killing an Egyptian was not even deemed unjustified or a "sin" in the sight of God. The Hebrews claim that breaking the law, especially in honoring one's parents is what decreased life expectancy. Later that was changed to only 70 years. It would all be related to the effect the earth had before the Flood and the general decline of the planet as a whole genetically after the Flood.
If you accept that Melchizedek could be Shem himself, then long life spans were still around even after the Flood. Noah lived after Abraham was born 50 years. Shem lived 502 years after the Flood. That was 152 years after Noah died. Sarah, the wife of Abraham was said to have lived 127 years, but Abraham lived for 175 years. In the last years of his life, he was said to father even more heads of families that populated and lived in the land of Canaan, and surrounding areas. Of course the Hebrews claimed that the "control" belonged to Isaac and the twelve tribes of Israel. The other families were given 400 years to do as they please, before the Israelites would come back to claim the land as their own. Not to mention that their cousins were the Moabites and Ammonites.
They weren't dealing with oral traditions, Genesis derives from Mesopotamian creation myths written down long before the Babylonian exile. And Genesis is not concerned with turning an oral tradition into a written one, its concerned with transforming a pagan creation myth into a monotheistic one.
Legend has it that it was Abraham (Hammurabi) that invented the alphabet and writing and knew the correct accounting of the creation. I am sure that trying to prove that would be even more difficult that proving Moses was real, as there were over 600 years between their appearances in history. It was Noah who taught Abraham as a child. Noah learned it from Methuselah. According to the genealogy, Abraham was born 300 years after the Flood. Noah died 50 years after Abraham was born. Moses lived about 1000 years after the Flood. Abraham told his sons Isaac and Ishmael. Isaac passed it down to Jacob and his 12 sons. There is no history accounting during the 400 years in Egypt. The Hebrews entered Canaan 1120 years after the Flood.
The first 400 years in Canaan were not that historical as they never completely took possession of the Land. It was proclaimed that Solomon began building the first temple 480 years after Exodus. Solomon's Temple was built roughly 1560 years after the Flood. According to dating the Temple was built in 966 BC. According to the above the Flood was in 2400 BC.
The Sumerians claimed they lived in the land which was completely provided for them (just like Adam?) from 4000 BC to around the time of the Flood in 2400 BC. The Flood changed the dynamic, and they had to start over again.
Of course there was writing before 538 when the exile ended. But what was written prior to 600 was not classical Hebrew. It was a different form of writing, like proto Hebrew or something else. Whatever they wrote, there are no traces of it left or any examples of it. If someone was writing down what the prophets said, they did not write it in the classical Hebrew as it is recorded now.
In addition, there is no record from the days of the first temple to verify that what was written later during the second temple is what was actually done at the time of the first temple. One can assume, but as for evidence, there is nada, zero, zip.
The written archaeological record of the Hebrew people begins after the exile when the OT was written down in classical Hebrew.
On the evidence being nada, zero, zip is not entirely true. Reconstructing the language through the study of language shows that it was preserved in the Old Testament itself. Otherwise the scholars would just be making up that there was a written language at all. There are forms of the language dated from 1000 to the time of the exile, but not enough to even reconstruct the whole. The Old Testament is one of the records around that give us an insight into the language.
Then there is the point that before 1000 the languages were not that distinguishable, but evolved into local dialects. The Samaritan Torah also retained some of the proto-Hebrew. Aramaic was already in use before 1000 BC. You are correct that we don't have any of the writings between 1000 and 400 BC, but that does not mean they never wrote anything. One view is that the actual writings have been lost. The other view is that the Babylonian exile did not really interrupt the ability of the educated class. They were able to keep on copying the source material in the Aramaic. The material was not changed, it was just written in the Aramaic instead. The material of Daniel is the earliest we have, and it was attested that they were given their freedom to carry on the culture and religious traditions as long as they did not go against the established edicts of the Babylonians. We even see that Daniel bypassed that and won the favor of the king, even through the various changes in state leadership.
The copying was not a major change in translation, but a shift in dialects. I think that it is an established feature that religious texts, which after the exile it was maintained that they were religious, were often written in a language that was different from the spoken vernacular. It was the exile that may have brought about this shift into Biblical Hebrew that was a "language" of it's own. At least until it was translated into Greek and the Hebrew/Aramaic remained with Judaism.
Even though there are not any copies in extant, the consensus still remains that writing was available and that it did happen. The exile was only 70 years, and even if the Babylonians allegedly may have destroyed all extant copies, that does not mean that the scribes ceased their activity, and very well could have had copies in their possession that were not destroyed. They kept the process going albeit the Aramaic eventually replaced the majority of the proto-Hebrew, but left examples that scholars have identified as being the same as the original. If it was totally made up, then perhaps there would have been nothing left, but yet there is. That may also explain that there could be no change in form after the exile, because the exile itself caused the change as a curse. Not wanting to loose the originals again, they strived to keep all copies thereafter the same, or at least kept comments to the margins, and leave the copy the same as the original. That would not prevent it being translated to other languages, but would at least keep the internal practice constant.
