I like what Carol wrote, not that you need to use the same words but it put so simply what we each tend to overcomplicate.
No is a complete sentence. A few more words make it kind yet leave no buttons left exposed for him to try to push.
"Keep it simpe" is a wonderful slogan in the rooms and in life. I needed to read that today myself, as a reminder that life is only complicated when I let my mind loose and welcome the committee that takes up way too much space...the "what if's", the "if only's" the "woulda, coulda, shoulda's".
Keep it simple Rozie. Helping him is helping his addiction right now. "No more" is clear and precise and very freeing.
Hugs