The proof only goes to dispell the idea that the book is consistent and complete.

Complete? How can any book be complete, if detractors are allowed to choose any topic to ask what it says? You might as well ask whether the Bible has plans for a FTL Drive and claim its believers are deluded if it does not. Obviously the "completeness" is in the context of their beliefs, not any particular measurement chosen by a detractor.

If they'd only say "we believe it because we want to, no matter what it says", or "we believe there's some deeper truth in there, it just needs a proper interpretation",

I think many believers go along with the second claim. The Bible has remained relevant to believers for 2000 years so clearly some interpretation is required/allowed along the way. Example- a rich man benefiting from his wealth after death is as easy as a camel going through the eye of a needle. The idea is relevant even to those of us who do not possess a camel. ;-)