I would do a practice letter of telling him he needs to go to rehab and post it here for feedback.

I just want to make sure I understand, you have never told him that if he drank again he would need to go into rehab. Is that correct?

FWW/BW (me)
2nd M for both
Blended Family with 7 kids between us
Too much hurt and pain on both sides that my brain hurts just thinking about it all.