I think that the line of where mythology ends in the Bible is probably a point of discussion as it's not entirely clear to me, and could probably use insight from someone better educated on this topic. I would hazard to say that this is not divided into fact and fiction, as it seems that the authors of the biblical texts did not/could not have such a world view. Literature, its role within a society, their conceptions of truth and meaning, all functioned very differently.

I would personally assume that the Adam and Eve story is also mythology for reasons similar to what you mention: nothing about the story is actually asking me to take it literally, and it doesn't seem to match our best historical records. So yeah, a literalist hermeneutic has all sorts of problems, and not just in Genesis. This is why most branches of Christianity, save the pronounced post-pietist and conservative Anabaptist movements, do not maintain this hermeneutical approach.

As C. S. Lewis famously stated, and I paraphrase, "Christianity is a myth that is true." To equate myth with fiction due to a binary view on the role of language as conveying either truths or errors seems to be a lazy application of reason. This is where fundamentalists thrive; that is indeed their worldview. It should be rejected by all persons because it is not very unintelligent. By that I mean not well equipped for understanding the world around us.