In my fourth year of my PhD on schizophrenia and I'm currently writing up my thesis. I'm procrastinating right now so thought I'd do something useful with what I've been studying.
And no, schizophrenia is not multiple personality disorder.
Edit: I have to get dinner and run some errands. I'm really enjoying this so I will definitely get back and answer the rest of the questions.
I don't think you would want to push him too hard since that might alienate you from him. If I were in that situation, I would probably speak with a health professional about it. If the extreme paranoia and delusions are really affecting his life, then that's what I would definitely do.