God is all means god is nothing. Anything that includes everything is pointless on itself. Besides, there is already a word for that - it's called the universe.
You are totally misusing the word "know". What is knowledge according to you? Does knowing I have magical healing hands means its true? You are totally mixing know and believe.
Science doesn't know the future, but it's the best and only method we know of to make attempts at guessing it.
What???! Again misusing the word know. It's not know, it's believe (or disbelieve). No one knows if gods exist or not exist since there are no evidence backing its existence or it's none existence. If there are people who believe there is a god and there isn't one, they are wrong. If there are people who don't believe there is a god and there is they are wrong too. Both can't be right.
There are things, like ideas or questions that can be both true and false. But things that are testable, and exist within the physical universe (and influence it in any way) cannot be both true and false. The existence of a snake skeleton in front of me right now isn't true and false, it can only be one of them. Existence isn't a trait that can be both true and false, it must be one or the other, otherwise it contradicts itself.