OK, what I mean by "detaching" is not saying things like, "Really? You are making her get you booze? It is dangerous outside." You didn't have to say anything about alcohol. If you felt you had to say something about the weather conditions, you could have just reminded him that it's dangerous outside and that it probably isn't a good idea to be driving.
"Detaching" means doing your best not to allow his behavior to affect your moods and actions.
Your biggest obstacle in all this is your husband. It's very difficult to set firm boundaries when the two of you are not on the same page. Have you discussed what will happen when he graduates? If I recall correctly, he graduates this year. Will he be expected to move out as soon as he's employed? I think the sooner you get this craziness out of your house the better off you will be.
Keep going to Al-Anon.