To answer your bolded question, basically, is outpatient treatment and AA enough for someone to quit, the answer is an unequivocal "yes". Some people do better with inpatient, but many do just fine with outpatient. It's not necessarily a lesser type of treatment than inpatient.
But the person's attitude is the key to the whole thing. At every AA meeting there are people who are only present because they have to get something signed for a parole officer or a judge, or maybe their significant other forced them to go. They stick out like a sore thumb. Is AA doing any good for these people? Highly unlikely.
If, on the other hand, your husband is really serious about getting help, then he can see a doctor in an outpatient setting and get medication, if needed, to detox safely, plus professional counseling. And the fellowship of AA can help him learn how to maintain sobriety. You'll know he's serious, in my opinion, if he gets a sponsor and works closely with him, works the steps dilligently, and stops rationalizing having even one or two beers as being okay. AA is designed for chronic alcoholics, i.e. people who cannot stop drinking on their own. Admitting that we're powerless over alcohol is the first step, and if someone hasn't truly realized this, the other 11 steps will have limited, if any, positive effect.
Have you considered going to a meeting with him? Going to AA the first time can be pretty intimidating. Why not find an "open" meeting and join him on his first meeting or two? And Al Anon might benefit you as well.
Best of luck to you.