There no set type of password that any one type of person uses, that said, people all over use stupid passwords. And celebs are people too, so i wouldn't be surprised to see firstnamelastnameDOB used for at least a few of them.
Again, it depends. That info could be fed into a wordlist as part of a dictionary attack, but if their password is "godsballs" then it won't do you much good.
Again, its possible. But odds are, not. Plan on them being not complete retards and having picked a password that has nothing to do with their personal life so that if they did and you get it, then you'll be pleasantly surprised.
Hope that answers your questions, but unfortunately most of what your asking is more psychology and a person's habits which varies from person to person so it's nigh on impossible to give you a straight answer.