Edjumacate me here, because I have never heard of a Christian who actually followed all of the levitican rules (no cheeseburgers, no bacon cheeseburgers especially, and so on; lots of severe penalties for stuff we'd never consider too serious today, etc) but....
Wasn't one of the new testament books at least in part a record of the explanation to the Jews and others that Jesus and his sacrifice had superseded the old rules and made them unnecessary?
I see your distinction about word of God given to man vs stuff written down by man.... but don't you have to believe that the word, in either case, got a little help in getting to your ear or eye? I mean there has to be faith the right stuff got written, and I don't see a big difference.