If the big bang could be proven, which it cannot,
When nearly 100% of experts in physics agree that the Big Bang happened, I pretty much consider it proven. Unless you consider yourself to be more knowledgeable than them. In which case, please offer your scientifically supported evidence for your alternative explanation for the origin of the universe and take your Nobel Peace prize.
than it also lends itself to being a miracle, something created out of nothing.
The universe emerging from the singularity is not exactly creation from nothing. There are explanations of where the energy came from. The idea that some intelligent creator was involved, however, is not taken seriously because it is not a necessary explanation. Just like Zeus is no longer necessary to explain lightning, as scientific knowledge increases, the necessity for the god explanation to explain the unknowable shrinks.
The big question is, what happens to the mind when the body perishes?
Well, since the brain is what creates the mind, I think the result of the brain ceasing to function is pretty self-explanatory. Granted, I humor the thought that the world is created by the mind; an idea referred to as "solipsism." However, I would not try and justify that idea as if any amount of logic trumps real-world experience.
The worrying part for an atheist should be, that maybe the mind lives on. rev9.6 "They shall seek death and not find it"
The real testimony as to the validity of Jesus comes through the Holy Spirit, which also is the only unforgivable sin, through experiencing and than denying this witness.
Yes. Your God is a prick who demands worship while hiding himself so well that any rational thinking person would doubt his existence, and then punishes them for not worshiping him with eternal torture. Sounds like a swell guy who totally deserves our admiration.