Sweetie, you are not throwing him away. You are taking steps to make your life right for you. Sometimes relationships don't work out and addiction or alcoholism doesn't even come into play. Think of it as; you are giving him a chance to live his life as he chooses. You are giving him freedom, you're not throwing him away. No one wants to be in a relationship that's unbalanced, unfulfilling, or full of misery and despair.
Stay strong. As hard as it is, this may be the best thing for both of you. Hugs!