Reading through the report, I was wondering about the part that said " lack of intimate peer relationships". We know he had a girlfriend, and a friend who he spoke to about feeling depressed/suicidal and cried infront of. While this could all be surface level, superficial relationships, that he was playing the part of a regular teen but it does also say "recent escalation in negative affect" so was he actually being truthful and himself with his friend? I wonder how his friend and girlfriend feel about him now? Imagine how strange it would be if he really did pull the wool over everyones eyes and this is not the AC they knew at all. If that is the case, I wonder if they miss him and how strange a feeling that would be now knowing what he did...
Sorry for the rambling. I think about this case all the time and have so many questions about this monster and his thought process which is so far removed from any normal, rational human beings.
I don't think he cared at all about her suffering and you're giving him too much credit, IMO. I don't think he has a split personality so much as there is the real him and the mask he used to go about day to day. A normal person see's paedophilia, necrophilia, murder and rape as abhorrent, shameful things but he does not seem effected by other peoples opinion at all. A "normal" person who had these thoughts in his position would probably have kept them to themselves but he willingly offered this information. Could it have been purely to shock the interviewer? Possibly, but I think the observation that he was irritated by the medical evidence she was alive when he raped her was a truthful response from him and he really is the evil monster that we fear he is.
IMO, I don't think he will ever be rehabilitated and I believe studies into psychopaths would back this up.
Again, sorry for the rambling I'm basically thinking "out loud". Now I'm wondering if it was nature or nurture as to why he is this way....