Even if scientists agree that the Big Bang is how our universe began, that doesn't explain how all that energy and matter got there in the first place.
I don't understand what you're saying. What's the logical reasoning according to which if something exists than it has to have "got here"? Why is existence something that has to come into being?
Also, I don't agree with your argument that atheism is a choice or an act of Will. Despite being an atheist, in the past I have approached christians and the christian church, read the gospel, and repeatedly attempted to "open myself" to God. You know what happened? Nothing. That's the only reason I don't believe in God, because there's nothing that gives me any reason to do so, not because I have an alternative explanation on how the universe works. (though I admit to never having approached any religion other than christianity).