You have to decide just how many times you want to take a chance on getting hurt all over again. You say you konw he'll start drinking again and that he is doing nothing to really deal with his issues. So, what are you going to do to deal with your issues? What do you want to happen in your life?
Splendra's comment about are you sure its love struck me too. Could it be habitual thinking to some degree? Are you in love with the fantasy man that doesn't really exist? Are you afraid to be alone with out a love relationship?
I discovered myself that I no longer loved my AH, that I was in love with a fantasy man who never really existed. That realization made it a bit easier to deal with all the emotions that went along with leaving him.