I take what Moses wrote literally as he wasn't writing as a prophet. He started writing the Bible with the Ten Commandments and it explains why God killed everyone (descendants of Adam and Eve) and everything on Earth. If you look at Moses times, he was under persecution as the Babylonian empire arose and led to some key events in Biblical terms such as worshiping false gods. They were an advanced civilization already with great resources from their rivers and they had much gold and silver to trade with and to use as precious metals. I think many could accept the Ten Commandments like we do today, but would not be able to obey and follow it. It shows that we all are not sinless; I think that's what people in Moses' time got, too.
Moses reports on things that happened around 2500 years before his time. Would people be able to believe what he wrote? I would think they could go back a few hundred years with some accuracy, but anything over a thousand becomes difficult. I think they could believe what happened in regards to a global flood from that period of time before. There was a mythological story regarding a large flood as the Epic of Gilgamesh and Moses wrote something similar of Noah's flood in Genesis, but I think he explained much more in detail. I would think there were people who did not believe Moses about it during that time as we have people who dismiss it as myth and use the Epic of Gilgamesh as argument. Here are the differences between the two from a Christian pov --
The Flood of Noah and the Flood of Gilgamesh.
I had trouble with the people's longevity when first reading it. However, things were different in those times. People could live for hundreds of years --
http://amendez.com/NAES/Noahs_Ark_Articles_files/NAS The Scientific Evidence for Biblical Longevity.pdf. Moses states God shortened their lives to around 120 years after the flood.
What about Adam and Eve? What key learnings are from their sin? One is the sin they committed was thinking they were "like God." This is what Satan as the serpent was able to tempt them with. The other was that we all changed from what Adam and Eve were physically to flesh and blood creatures, even to this day. That we are all born of Adam's sin. One more big learning would be that God formed Adam out of dirt and gave him life through his breath. We find science backs it up today as the supernatural of life spirit exists next to the natural.