Therefore, just as sin entered the world through one man,
That would be a wrong analysis. Sin was already in the world: the serpent. Or, if you want to call it Satan - which frankly is kind of silly, but whatever - then still, that sin predated Adam. You xians like to think of Eden as perfect, but obviously it wasn't. The serpent's/ Satan's sin was present. And who allowed it there? yhwh. not Eve or her slow witted mate.
As I've said, I have to get my ego out of the picture
I'd say you failed horribly at that. You come off as quite arrogant here, which is naught but ego.