MelissaTex it is time to remind yourself that it is not you it is him. When his is calling you names it is because he now sees you as the disciplining parent who is catching him in the wrong. You can either continue to take this seriously or just let him rant and walk away. He can scream but just like disciplining a two year old you can step over his flailing body and get on with your life. From your letter two months ago you said that he has a number of strong addictions and he goes to counselors and such only to hear them pat him on the back and tell him he is doing the right thing. Stop being a reinforcer for this ego trip he is on.
Hopefully in the meantime you are pursuing employment counseling and looking at freeing yourself from this growth that is growing on you. You and mom need to come to an agreement for paying back the money and if mom can afford more rent then maybe she could pay more every month. Also if he is not cleaning windows 3 or 4 days a week maybe you can take over and help make the business more thriving while you look for something else. Maybe even look at expanding this into other areas so that you can get an income out of this as well. And when you do split up you could end up with half the business because of your contributions to it. 