I am sorry you are hurting. It is always hard in any break up. you want what you were promised, a future. you have dreams and plans and those have to be let go. it is so hard.
You want closure from someone who cannot give it to you. you want to talk and understand why, answer your questions. Your guy cannot give you that because he honestly does not know. He does not have the answers. He is caught up in his own thing oblivious to his actions except shame and guilt about it I am sure. He is ashamed because he drinks and he drinks because he is ashamed.
Only he can help himself. You cannot do it. It is incredibly sad to see someone self destruct, but you cannot save him alone. He will drown you as well.
Hugs to you.