I'm not going to support my aging dad
Why don't you want to support your dad?
I found him preaching to me with his old school friend. On top of that I find the friend very annoying
Parents can be difficult  sometimes but we should still care for them especially if they are getting old. They need a lot of care and it is our responsibility.
I just can't deal with his shit. He thinks I owe him something
I would suggest you talk to him. Set your boundaries for how it will be with you taking care of him.