How do I get Dad help without him knowing?

I wish there was a magic answer for you. Many people have a similar issue. Does you father live alone? It's possible that if you called Social Services and asked for a welfare check that they'd see he shouldn't be alone and then he'd have to make some changes. As a family member, it's hard to force any adult to go to a doctor. Hard as it is, if SS can't do anything about it, you may have to wait it out. He has rights and unless you can prove in court that he's incapable of taking care of business, there may not be much you can do on your own. Hopefully, adult protective services can help.
Take care,
Carol