I agree we can't be diagnosing your son, or even you. But from what you originally said, he called you a ******** something or other, I'm guessing, an f n b****? I've got 2 sons, one an adult and one not. I tried the hard road, the soft road, whatever I can find in between. Bottom line is neither had respect for me no matter what I tried.
Giving in to his wishes at 24 is, in my opinion, not a good idea. He is possibly manipulative, and in your words, at least verbally abusive. I wouldn't put up with that. You've decided to help him financially because you can. That's fine. But I do think many here have very good insight and very good advice. It's your job to take what you think will help, or leave what you think doesn't. I do know, the more you give people, whether in a romantic relationship, sibling, or other, such as friends or children, the more they take, and it is not the answer. He needs to contribute financially, and that is only my opinion. There are ways for people that age and with college degrees to handle their own life. I'm glad you are trying so hard to help, but, I'm only going with my experience. Best wishes.