Yeah, I wouldn't even know where to begin to reply, since, yes, as you say, I do not consider Gen 1-3 to be historical. I accept the Torah as the religious text of my people, and am observant, but not all of those laws have anything to do with ethics. There is nothing specifically unethical about having a wool suit with linen button holes.
I think that our capacity to think morally has evolved. The foundation for moral thought is empathy and a perception of justice. I think by and large, people make moral decisions unconsciously, and then once having made those choices, come up with conscious rationalizations why they did so. This is why you have people saying things like, "It's just so wrong. I don't know why, but it's just WRONG."