Hi, FG, and welcome!
My suggestion is that you (a) stick to your plan no matter what and (b) get yourself to some Al-Anon meetings.
Don't worry about the length of the program. Three weeks will get him off on a good start, provided he is motivated to stick with it. If he isn't, then four months wouldn't be enough.
You worry about taking care of YOU. Let him and his treatment professionals worry about HIM.
Hugs, and if I were you I'd have a backup plan in place in case he refuses to go on Friday. I.e., a plan to leave. You don't have to (and probably shouldn't) share that with him, but you alluded to his abusing you. Whether that is physical or emotional abuse, it isn't acceptable and you shouldn't have to live in that situation. I suggest you also contact a domestic violence counselor for some help on that.