We alcoholics are a lovable lot until you come to realize that we are far more in love with alcohol than the people who love us. As in all relationships 3 is a crowd. I am very sorry you had to discover this the hard way. Unfortunately his first love is drinking and you are along for the ride as long as you don't interfere. Maybe someday he will sober up but until that day a relationship with an alcoholic has very few positives.
You can forgive him but you deserve so much more