If the guy is a grown man, supporting himself, he must do what he must to either accomodate or be done with his father. The most another person can do to help is to encourage him to be painfully honest about his own motivations and thinking, and supportive of whatever decision he makes. Good luck. That is a tough situation.
get another policeman involved and if hes under 18 call cps
Put a Contract out on the Dad, show you care.
the only way this guy will stop beating his son is A) the police are called B) this guy beats his dad and defends himself
let him be your roommate and be the one to answer the door and phone till he can get the strength to confront the guy