You really have nothing to feel guilty about OP, in fact you have been enabling him up to now as you haven't been giving him consequences for his continuing failure to address his addiction.
Atilla (who posted above) recently posted a link on another thread about addicted partners, it was a long piece about the "drama" or "theatre play" of the addict and the enablers around them. Really very eye opening, but I didn't save the link. Perhaps @AttilaTheMeerkat could post it again as I think it would help you address the guilt he is pushing onto you. Which you absolutely should not accept.
Shut these conversations down when he starts. Find a phrase to use, one he can't possibly argue with. Something like "I have loved you as best I can, but I hate your drinking, and I won't [not can't] continue this relationship to the detriment of my own health and happiness. I've told you it's over, I won't be changing my mind, so save your breath."
Do not believe any of his bullshit and promises to change. If he genuinely does want to change, then let him change alone, and find sobriety alone, and if he then wants to contact you in the future - after, say, at least a year of sobriety - then maybe, just maybe, you might consider sitting down with him then. But don't tell him that now.
It is actually kinder to make it very very clear to him that you won't be changing your mind, so he needs to accept the reality that he is now single and deal with the practicalities.
Are you living together? Can you move out? Don't wait for him to take action as you could be waiting forever.