However, who said there wasn't other universes before our own that have gone through big bang/big crunch cycles?
Who shows there are, may I subject your speculation to the same evidence claims? You merely posit an alternative. We can invoke Occam's Razor here. God is perfectly simple, and explains everything about the universe. The universe is incredibly complex, and explains nothing about itself. So Occam's Razor would seem to favor God over some infinite set of universes, existing forever.
Or let me argue this from the other direction. You state that nothing in the universe is eternal, yet something must have caused it, and that is defined as "god."
The OP presents a set of rational/philosophical arguments for a First Cause, something that I (and many others) call "God". (Science itself rests on rational/philosophical presuppositions also which cannot be scientfically proved either, but to get back to the point.) You want scientific evidence, something that scientists themselves know they will never be able to get, because science cannot go past the beginning. In fact, science can't even observe all the way to the beginning, since we cannot see any earlier than the first Planck second; the laws of physics not holding before that point.
Why is god automatically eternal? That's another case of special pleading. No evidence is presented as to god's existence in the first place, let alone it being eternal.
First research what eternal means. It does not mean lasting an infinite amount of time. Time came into existence along with energy and matter in the Big Bang. Something that existed before Time, is not in Time, is eternal by definition.
BTS