Okay that's a lot to process. Incestuous affair?
Luke beat Darth and maybe I'm a broken record but sometimes guys don't want to crush their opponents, IMO. He didn't want to slay his son. And wasn't there more to toughen Luke up between Ep 5 and 6? Or was that the three months? I remember a "bridge" novel or something developed later.
But you're right, it is a bit of a stretch in the unlikely realm, even as hard as GL worked to make "bad motha" Luke in ROTJ.