Thanks for the kind words - I don't mind at all
Being a friend does not necessarily mean being an enabler.
If you want to remain friends and not just walk away - I assuming you do - I think it's perfectly acceptable for you to set reasonable boundaries for yourself, and also to let him know what kind of behaviours you'll find unacceptable from him.
I'm not sure any words from his Dad would have any greater effect than words from you tho - if the father is already worried presumably he's already discussed this with your friend?
I know it's difficult - we want people to be ok, we may even want to fix things - but sometimes that's really not what our job is.
I just wanted to say hi and welcome you really.
There are others here with way more experience in these situations than I have, and I know you'll get a lot of great responses here
D