So your claim is that tge universe had a beginning? To me, the universe having existed forever, and it starting to exist at some point with nothing, not even time before makes just as little sense.
Really, things existing at all makes little sense, it would make much more sense if nothing existed. But that is at odds with what I observe.
So you’re just redefining God. That’s fine, but it’s not helpful in a discussion where people assume by default you’re using a common definition of God.
Both science and religion try to answer the question ‘why’. Religion says ‘a God did it!’. Science says ‘I don’t know. Let’s observe our environment and see what theory could best explain what we see. If anyone later proves me wrong, I won’t be upset, I will be glad that I understand more.’
You can in fact prove the non existence of a thing that is logically incoherent. Obviously the default position to be is agnostic, but you can actually disprove the existence of specifically a tri omni God via the problem of evil.
If an all knowing, all powerful, all loving being existed, we would not observe evil in the world as it would be knowledgeable enough, powerful enough, and care enough to get rid of it. We observe evil, so this being does not exist.
Of course, a lot of behaviour of God in the bible suggests that he is not all loving, which would trivially resolve the paradox, but a lot of Christians believe in a tri omni being anyway, which makes my prior argument non entirely irrelevant.