I have a few thoughts on this. For context, I'm a Christian with equally big interests in science and theology.
A. Remember that scripture wasn't written to us 21st century people. It was written in a context, in a language, at a time, for a culture, all different from what we have today. So for us to understand scripture we have to understand the context surrounding when it was written. This means hypothetical differences also need to go through this filter. For your examples of Native Americans or bacteria, what would the early Israelites have done with this information? I'd say it would have been seen as a weird side detail likely wouldn't have survived being part of an oral tradition. Especially the bit about bacteria, since they didn't have a word for it.
B. I don't think that's the point of the Bible. The way I describe it is "God's biography". A bunch of authors all wrote their part to try to communicate who God is and what he has done. These authors all had the chance to live close to God, and got pointers on topics to write about, then they all write about God.
C. I've had a similar conversation with some of my friends. We were playing "that's a question" (party board game about guessing what answer this specific player will choose), and the question of "would you prove God's existence/nonexistence?" came up. We're all Christian, so we were talking about proving that God does exist, and we basically came to the answer that God has clearly built the world in a way that does not absolutely prove his existence, so he must have chosen to not prove it for some reason. Our best guess was that if it was proven, a lot of people would follow him out of obligation instead of love.