Hi Kate1 I understand how you feel because my mother went through hell with me.
Unfortunately there is no quick fix because an addict will only change after hitting rock bottom and the more that people are enabling the longer this will go on. Personally knowing that I could use guilt or pity to get what I wanted from my mother despite already losing eveyrone else kept me in the cycle. I have been on the receiving end of what i m going to say and he will say horrible things and try to play the victim but stay firm. You need to be tough and offer any emotional support he needs but no more financial assistance. He will resent you qt first but the goal is to break the cycle and to still be able to have his mother for advice and guidance.
It is not easy but you need to make him responsible for his own actions and to make him understand what he stands to lose.