Moses did not read the story of Etana and incorporate him into the OT. If anything, after the downfall of Babel and the confounding of the languages, different groups having the same language gave different names for Nimrod, he was a real and powerful person.
Moses was shown Nimrod by vision as he had been shown the creation and Adam and the prophets that followed Adam. These were shown in vision to Moses directly from God.
That is where an issue occurs at, whether anyone one religious group is right or whether any one religious group is wrong. My statement of what happens after death is based on your belief and is very relevant to your belief. To clarify if you believe in reincarnation this is your belief, if you believe in heaven or hell this is your belief, either way someone will be wrong and someone will be right. No one knows what happens after death at all; hence it is based on your belief system.
As far as restricting what happens in the afterlife, and the progression in the afterlife, once again goes back to either your belief is right or someone else's belief is right, hence making your belief wrong. So it really doesn't matter what you believe versus what someone else believes, because there is no sure way to tell who is right and who is wrong. That was my point the entire time, regardless of what tradition you follow or book you read, the best possible guess is going to be based on your religious or ideological beliefs. No one can prove there is an ultimate heaven, hell, purgatory, reincarnation and so on, because differing ideas do not equal the same outcome per the belief, hence why humans to this day are still trying to figure out what happens after death.
St. Moses pens the Deuteronical texts about 1700 BC, most scholars would agree. The issue is whether or not Nimrod is shown as Etana, Moses would have written those stories which are reflected in earlier cultures. Such as when Abraham came from Ur, and left to Canaan. But, per what I posted earlier we see Nimrod from differing aspects from each religion such as Judaism, Islam, and Christianity, yet we see Nimrod with characteristics of Etana. Etana is a Sumerian name, while Nimrod is a Common Stock West Semitic name, St Moses is a Common Stock West Semitic name as well and not a Sumerian name, hence the writing of Etana shown as Nimrod.
Also, St Moses would only have to understand the language that is Semitic based and not Sumer based, so I wouldn't expect that Moses "knew of Etana" in that fashion, but he would know of characteristics, the same as Etana.
Concerning the tower of Babel and its languages being split, there is in Sumer a much older Cuneiform of languages being divided by Enki in Sumer literature. Also, the Babel tower is falsely identified with Ziggurats, so in Southern Mesopotamia there are about 30 of these temples (Ziggurats) from Mari to Tell-Brak and from Ur to Eridu in the south, and so on.
The Hebrew's would have used the term migdal in a military setting and less of a term for a Ziggurat. So it is most likely that the Israelite's would have not known what these Ziggurats’s were to begin with. The description of the tower of Babel occurs in Babylon, which is in Southern Mesopotamia and where Ziggurat's would lay. So it is less likely that the Israelite's were familiar with any story of a tower of Babel and its fall. But, not foreign to Moses who could easily compare a Ziggurat to a Pyramid, though the Egyptian culture is not inspired by Sumerian culture at all, yet by the time Moses is in Egypt there is Southern Mesopotamian oratory legends, stories and so on that abound.
The claim of divine inspiration to Moses makes sense, since Moses appears in the NT as Israel's lawgiver (Matt 8:4: 19:7.8; 23:2; Mark 7: 10: 10:3.4; 2:9: Luke 2:22; John 7: 19.22.23; 8:5; Acts 6: 1J. 4; 13:39) he would have to claim divine inspiration. Hence he would be truly considered an Yahwehistic and dabbled in Yahwehistic occultism.