I'm so sorry, you've got way too much on your plate and you're in my prayers for sure
For what it's worth, I don't think that you should just "cut him off", but maybe tell him that you will always be there to listen and to maybe give some advice, but he needs to work out his own drug/girlfriend issues. I've witnessed the toll that my ex husband's drug/criminal behavior had on his parents, they were always bailing him out of trouble and rescuing him time and time again, only to be kicked in the teeth for their kindness
To this day, they STILL send him money, meanwhile he does nothing for our son, or his two other sons he's fathered since then. Tough love is the way to go, and that doesn't mean that you have to give up on him, it just means that you have to stop doing things for him and just be supportive without getting sucked into his problems. I'm sorry that he can't work, and I'm sure that is taking a huge toll on how he feels as a man, but the drugs sure as heck aren't going to help him heal.
BIG HUGS!