Ok so this is not a theory on who is RJ but more of how the hell did he do that? and my theorys on them...

The happy memory thing?... must be when PJ was in mental hospital he must have been heavily sedated at some point & can not remember telling that doctor Sophie Miller about it. Or he was hypnotised in there by someone.  Its the only way!! people can not see or read your mind thoughts.  Rj is a very clever cunning psychopathic killer yes but not superhuman. got to be simple answer.

knowing the whole 7 list thing...? this im not sure on and this is a bit of a long shot but if i had to take a guess the only way i can see how RJ knew about Janes list is PJ  only started making his name list after Lorelei told him about the hand shake, so maybe she played him and this was RJ plan all along. If PJ can make a list in that amount of time then why can't the clever evil killer do so too.  Maybe lorelei was told by RJ to tell him that information, this would explain why she out lived any of his other follwers and why she was in jail for weeks and not 6 feet under. Maybe lorelei already knew rj killed her sister or even ask him to do it and she didn't care like she pretended too with those 2 people she tortured, it was all part of game to con Jane.  Why? Rj would want Jane to know this info I don't know? but maybe RJ just wants to end the game and kill him now.

I realise that is bit much and prob not even right but RJ and Jane are so alike & clearly intelligent and we all know that jane has no life these past 10 years and so anyone he shook hands with is cbi/work related (mainly) and RJ could easily windled down the list of 7 names like PJ has & he knew jane was trying to do so too. i think RJ may have come up with the 7 names before jane did and made that video then, before killing lorelei as she had served her purpose in his game.

I'm not saying i'm right but just wanted to share and this is what i'm thinking right now after series 5 and I'm sure when series 6 is back on I'll change my views or the writers will go down a totally differ route with the list thing and i'll be totally on the wrong path i'm sure.