My input is to take him out of the statement altogether. It is about you after all...
I'd say something like:
I can't be with anyone who drinks and isn't willing to do anything bout it. It isn't what I need in a relationship. I need someone who takes action about a serious issue affecting their life. It upsets me to see you do this to yourself so I am telling you that I need to do what is best for me.
Putting the focus on the other person when we are the ones who are having the difficulty is problematic with or without a drinking problem. It makes the other party dig their heels in and get defensive. It comes across as an attack no matter how delicately it is worded by the one needing the break. That is why you can only use "I" statements. "I need", "I want", etc.
My two bits! And power too you cuz your strength does come across.. Stay strong!