ichabod, things are probably different for your son that they were for your husband at the same age. He's getting expert age-appropriate treatment and has the best chance of recovery.
Not all A's are the same. He drank to relieve his feelings and, without getting your hopes up or predicting what will happen, the treatment for depression might take away the need to drink.
My nephew went through severe anxiety in his senior year, got expert treatment, and, although he will always have the condition, has learned to keep it under control and monitor himself. He now has a lovely wife, a great career and a cute little boy.