I need help convincing my dad to get divorced and go his own way.

My mum left us when we were kids and my dad raised me and my brothers on his own. he has a serious job and always made a lot money, he pays maintenance to my mum who lives 300 miles away with no kids to look after in a house he bought. When we were young we did the funniest shit and when we got older it got even funnier. We got drunk went to gigs and trashed the place, got in trouble load of times. We went to Amsterdam and got high as shit on a boat for three days. He is unlike any other dad.

Now we are all adults, He has married this bitch that has beaten him into a shell of his former self. He pays for her kids to go to college, bought her a house and a car for her and one for each of her kids. She doesn't work, he now has two jobs.

He is fucked, on anti depression meds, doesn't sleep and she doesn't let him do anything. She just emotionally blackmails him. He doesn't realise it's all her fault.

How do I convince him to get divorced again?