This is the person he is today. He is showing you who he is. What kind of employers do you have that host an 'all you can DRINK' party? No one cut him off? That's pretty outrageous.
A person doesn't have to drink every day to be an alcoholic. Someone who can't stop once he's started falls into that category too.
The whole purpose of dating as an adult is so you can find out if the two of you have enough in common to make a life together. You are seeing now what that life would be. It sounds like this is not the life you want. It's perfectly okay to forgive someone and not have him/her part of your life.