Now he did not say he would go back to church if I could prove it. But he did juxtapose those two things implying that his doubts about the Bible had caused doubts in his faith. Now no one can really prove the Bible true. As I commented as you study Biblical Greek you find there are other extra factors that confuse things even more. ONE MUST ACCEPT GOD ON FAITH.
I think the bottom line is you must accept the claims of Jesus to be Son of God and fully man, that he came to earth died for our sins on the cross and then God raised him from the dead in three days.
But by this man's own admission he did once believe and did attend church. This whole doubt story is a smoke screen. He simply does not want to change his behavior. He understands (somewhat rightly) that he cannot continue in the behavior that he is doing if he honestly wants to be a true Christian.
Someone once aptly said, he has been inoculated to Christianity. Now he knows the claims, even knows the truth of the claims, but he can resist because he likes life as it is. The pearl of great price that a man hid and sold all he owned so he could buy, this man has found too expensive. He knows its worth but still can refuse to buy it. So he uses this excuse that the Bible cannot be proven to be true. In this he is absolutely right. I think you come to faith first and then God reveals all.
He then throws in things about science. This morning he posed a question. What if another planet was discovered with people worshiping a different god? That's a lot of ifs. This is a conditional based on an untrue premise.
Based on experience and faith, there is sufficient reason to have faith in the cross and resurrection of Jesus for anyone who wished lay down his life. But if one does not want to give his life he can find reasons, superficially good reasons, to say he cannot believe. But it is all a crock, a pretense, a smoke screen.