I always had the impression that Norman killed
Lila in the cellar
killing Mrs. Spool at the end. Who I always thought, (Spool)didn't kill anybody in Psycho 2
BTW, Psycho II is one of my favorite sequels. And I'm also looking forward to the Blu-Ray too.
Even though I have seen Psycho 3 (and 4) I really don't remember the film that much to comment on those points you brought up. Sorry about that.