I really liked the quote from the guy who lost 2 dozen friends in School(could you Imagine) "He needs to talk with someone--talking will be like letting poison from a wound--but he has to decide when and to whom on his own terms"
Sometimes just talking your problems out to a person to just for the sake of saying it can help you understand your problem, and that's more beneficial than advice. The son is obviously reaching out when he did the Facebook post, and just wants someone to know hes hurting. I think the best way to handle this situation based on what I read is that the Dad could be more assertive in saying he's a positive, reliable presence for his son. In doing this he will eventually open up to the father and vocalize his pain, and be a path to understanding how to handle the situation.