Hi Nicola,
I don't think you are weak at all. You have hope, and there is nothing wrong with that. Hope is what keeps me sane in dealing with my CF, and I am sure I am not the only one.
I have been in similar shoes as you many times before. Hanging on to a relationship with the hope that things will work out ok, even though I knew I was not in a healthy relationship. Well, none of those relationships worked out, and looking back I realize they did more harm to my health then they did good. The emotional roller coaster is not good for either of you.
The guy needs to stop the dependency on alcohol. He needs to do some work on himself before he can come to you and be in a healthy relationship with you. Doesn't mean that you can't be with him in the future, but right now, he is more toxic than good for you. You need someone to love, support and respect you at all times, not just when they are sober.
Remember that all of us here on the board are here for you. We send you big hugs!!