How do you know? The bible is unreliable by your own admission. So how do you know what he said?
It isn't that I think the Bible is unreliable. It is that someone who is not Born of God does not have the Spirit to direct them to understand it or use it correctly. (and no, unlike the JW belief, I am not part of some small group of Christians who are the only ones to correctly interpret things, see 1 John 5:1)
There are many true words of God and Christ in the Bible. Then there are things that David said, or things that Lot did, etc. that God doesn't necessarily approve of. Just because God wanted something written down is not the same as Him saying it. I just think that there are also words of people and recorded history that God does not necessarily approve of, and there are also things that are misunderstood. The problem is when someone without the Spirit takes them the wrong way or out of context. "the dead know nothing at all" is way out of context. It wasn't meant to be a true statement! Jehu tricking people and slaughtering them? That is just history, not something we should copy. Paul saying that women should be quiet? Numerous explanations. Many Christians do research on these things because they know God. They know that these things aren't to be taken at face value. And it isn't difficult to figure out really... Christ himself told us what to think of the Mosaic Law, and in the OT when God said something, then the Bible says that He did. HTH!