Interesting topic! There are not many stories written about Men in the service of the dark lords, even though that area gives writers plenty of latitude to create new cultures and explore points of view which are missing from canon. In your summary, you did an excellent job explaining why the mythology is so different from the account of Middle-Earth's creation described in the Silmarillion, which I found very clarifying. I also liked your "implications" section that imagined aspects of these cultures we don't see in canon--what a wonderful idea. Fascinating dietary restrictions, views of "light" and "dark" races, etc. They work quite well, and of course religious superstitions are very, very human.
My only criticism is that I found the first part of the story difficult to read (which is also my problem with the first part of the Silmarillion--I don't particularly like creation myths, especially creation myths of fictional places). I would prefer if, rather than having a separate "Implications" section, you'd intersperse sections of "implications" into the body of the creation myth itself. That way, we could read about the cultural ramifications immediately after we'd read each part of the myth.