Dang son, sorry to hear all this. Hope it works out the best for all involved. Your hardest job will be to convince dad that as long as he is enabling them to continue their current lifestyle, they will never have any reason to change.
Dad must be convinced that in order for them to accept change, they must see a real reason to change, and he must come to understand he's the reason they see no need to change. Sometimes it ain't real pretty by the time they see the need, but it's the absolute only way.
And everyone suffers until he (dad) sees and understands that.
All the best !!!
