Contrary to your thread title, you do a lot right--you are a loving mother, extremely considerate and generous, and I can see through your words to see that you are probably friendly and great in social settings.
I identified with your behavior--I have an AH and an alcoholic brother who think of me as a cash cow, and they have every reason to, based on my own willingness to just dole it out upon request. It's hard. My brother says he only has $20 to get him to the end of the month. AH "just" needs $20 a day to feed his addictions and his friends.
And I feel like I so badly want to be the third leg on the two-legged stools in my life who have such a hard time standing by themselves. So I get it--but I've also learned this is a PROBLEM I have--it's not a SOLUTION for the person I'm trying so hard to support.
Imagery helps me a lot, and when I have a hard time detaching from sullen, mean abusive speech, I think of that spiritual goal of being like a rock in a river. Because I typically am a "go with the flow" person--I literally go with the flow and just absorb all the flotsam and jetsam of the feelings of people around me.
So I have to recognize when it's time to just be the rock and be still, be solid, and don't be swayed by externalities.
If I can't do that, it's up to me to detach physically, and not answer the phone, and go out and do my thing and leave others to theirs.
I know it's all so hard, but YOU did nothing wrong. He owns the problem.
Good luck to you..