The reason I suggested an AA meeting is that there, there's no expectation he would have to do anything but listen. No "participation" required. In fact, it's usually discouraged for visitors to share at an AA meeting. I'm suggesting it because it might shed a bit of light on why people like his dad keep doing the same things over and over--things they've been told not to do. Not that he will completely understand it--really, only another alcoholic can--but to see that he dad isn't unusual, that it's not that he doesn't care about him and his siblings at all, but that the addiction is so powerful that it overwhelms everything else.
Just a thought--you know your kiddo better than I do.