It's been my experience that you can't change other people. From your comments it sounds like he has a great big character flaw. Being hostile or verbally abusive to you is something you can change only by removing yourself from this situation. His son needs an adult like you or his mother to intervene on his behalf if you think it's needed. If this man can't use the same self control (with his temper) in his home with his loved ones as he would use in public, perhaps you should rethink your situation.
Slap his hand down and explain that picking your nose during dinner is rude and that flicking them on the waitress is wrong. Blowing up balloon animals at funerals isn't as great a career as he thinks. Asking your mom her favorite panty flavor. Yes you can teach younger guys new tricks