An extensive post like this I can't leave without an answer.
Grade: posts like this help us both to improve the mod and to get a morale boost. Thanks!
Thank you for your reply. Allow me to follow up with an update with a few more comments and even bug reports.
I found that my game crashed that same year because I was building that bugged Guilds building. Reloading and changing production fixed that problem and I can now play 10-25 turns before it crashes again, which is quite acceptable for now.

The game is currently up to the year 1725 AD IIRC.
UNITS - The units are fine and I only have two comments: 1) There exists some units to which there are no counters at all. These, in particular when experienced, will be impossible to combat and be victorious over. Also stats for various units seem fine, perhaps something could be done with these particular, unstoppable units. 2) I assume that units such as the Levy are desperately put together last-ditch defense type of units to be quickly and cheaply produced. As they are now, they seem slightly too powerful and too expensive. I found myself tempted to replace all my defensive units in all cities with Levies. These units should not be as good as the standard military units of the time. I'd, in the case of the Levy, and its follow up units, decrease its combat value by 1, or more in the later units, (making it sort of a bad early gunpowder unit as the graphics seems to suggest) and also make it slightly cheaper.
RESEARCH - Research seems to be too expensive. I like the proposed changes that medieval research be made somewhat cheaper and the economy being boosted by 10 %, but it seems something more needs to be done. It might be a good idea to scale down all research costs by the same factor as the number of inventions was scaled up. It might also be a good idea to allow for research exchange as part of some high-level diplomatic invention. Tech stealing as it is now works adequately.
GAME SPEED - Starting from around 1492 or somewhat earlier I'd have liked to play the game more slowly. Instead of 4 years per turn it would have seemed better with 2 years per turn to really be able to discover all the technology of the era plus to be able to fully experience these important centuries. Decreasing the game speed up to modern times (where game speed is good) makes up for the the somewhat too expensive tech research.
IMPROVEMENTS - About the Monastic Order; it seems much too expensive for what is basically a poor hunter's cabin. The price would be acceptable if it did something more, like what I'm proposing below. In addition to the food bonus (+2 food IIRC) it has two negative sides to it, and decreasing the -10 % wealth to a -5 % wealth only would seem to be a necessity. If the downsides are kept, however, it could actually be a multi-function facility by making the food bonus +1 only, while adding either +1 Health (monks were experts at plants, herbs etc. and had some useful (and not so useful) ideas about healthcare) or +5% Science (monks very masters of literacy, copied lots of books and spread information to other orders; this is also a partial fix to the slow research problem). Also, a bug report: Temple of Artemis seems to give +16 culture! At least it says so in the leftmost list of improvements when I check Delhi where it was built. This value should only be +8 if I understand this correctly.
DIPLOMACY - When I eventually reached America I had the pleasure to greet the Incas by the following statement: -Your head would look good on a pole!

However, I soon found out that the three civs in the New World were very powerful, and instead opted to join the Americans in a war against the Aztecs, who were the weakest. I'm telling this because I was first greeted by the Americans with -You declared war against our friend! when I had, in fact, never even met the Americans before (he was, of course, refering to the Incans). This was some time after, but the perfect memory of the computer civs should be removed if possible. In the course of a full game most civilizations will hate the player because almost everything you do makes relations worse. An alternative is to make a few more actions available that actually boost relations significantly, which would make it possible to obtain at least a few friendly civs.
Looking forward to more Total Realism playing and the next version!
Sincerely,
Peter Masterman