I am sorry for what has brought you here, and sorry you've been struggling with this for so long. Many of us have been and are in your shoes, so you are in a safe and wise place!
I agree with everyone's advice and second it wholeheartedly. NarAnon meetings have saved me these past few years with my AD, now in recovery. But I keep going every week and will do so for a long time to come, regardless of her situation.Now I am going for myself--to learn from others, share hope, work on myself, and be in a room of people who understand where I have been in ways many other people never will. Let us know if you can't find NarAnon in your area, as there are other kinds of meetings available for family members.
Keep coming back and keep reading -- there's so much to learn here!
One more thing: it is perfectly fine (and best) for you to create healthy boundaries around interactions with your AB and even your parents. F.O.G. can be so powerful and can keep us stifled and in crisis for as long as we let it. He is an adult now. So are your parents. And so are you...free to do what you need to do to live a happy and healthy life. Take care!