hm......getting better. As for the eden part, weren't adam and eve thrown out of the garden when god found out they had eaten from the tree? so wouldn't cain have been born outside and not in? maybe i'm just getting mixed up, but i do know that besides those two in the garden i THINK that lilith and naamah resided there. not sure......
as for justifying the crazy edinians personalities. That is definitely going to take more story elements. You are going to have to make them a past or a reason for being the way they are to justify them. Maybe there souls are lacking an element that the original humans had, or maybe they are the spawn of lilith or naamah who were made of sediment instead of fine dust(i think that's what it was) like Adam. OR maybe they are the true image of God(if you would like him to be an all around good guy) Things like those will make your story complete.
Maybe this babbling is a little crazy, but I'm half asleep, I'm still tired from the MTAC, an anime convention, so I might be a little off today....
good luck