I have the same issue with mascots, I can't get one to join my greek house. I don't know if that's normal, though. I haven't tried moving the mascot into a normal household.
For the poster having trouble getting the motivation to do a giant sort out, I'm just writing a tumblr post about this, I'll edit and add the link when I'm done ^_^
Backups - you should back up Neighbourhoods, Downloads, SavedSims, and if you have lighting mods or custom stairs then you might need to back those up too. Plus inteen has a file somewhere else, I don't remember where off the top of my head. If you just put a NH folder into a vanilla game without the correct mods, you can cause corruption.