I think FireSprite is right about asking what you are getting out of this relationship. You wouldn't have stuck around for so long unless the dysfunction in this relationship was somehow "working" for you. Before it starts to sound like I'm just snarking at you, let me give my example:
I was married to ex for over 20 years. During those years, one of the unhealthy dynamics (they weren't all unhealthy - there were some good ones too) was that I was the one who needed "fixing" because I was "damaged" from a not-so-great childhood and as a result suffered from depression. This "worked" for ex because it meant that he didn't have to confront his own dependence on alcohol or take seriously my attempts to get him to quit - he drank because it was such a strain being with someone as "unhappy" as me, and besides, who was I to criticize him when it was clear that I was the one with "problems" in the relationship. In hindsight, this is pretty twisted.
So it "worked" for him. But it also "worked" for me, because it meant I could count on lots of sympathy when I was stressed about something or when I felt anxious or depressed, and could reap the benefits of someone always telling me that they felt sorry for me because of my childhood. It enabled me to stay in the "poor-me-my-parents-weren't-very-nice-to-me" place and not move forward and past it. That was pretty twisted too.
So I did get some benefit from being married to an alcoholic. Unfortunately, what I got was toxic to me - and once I figured that out and didn't want to be in that role any more, my ex pushed back hard, and eventually it was all over (he unravelled rapidly after I left, suggesting that it probably wasn't me who made him drink, and that in fact I had been "overfunctioning" during the marriage to compensate for his addiction and shielding him from the consequences). (Obviously there was a lot more going on with ex's addiction and the dynamics of our marriage, but this was an important piece).
What I've learned is that I am much happier, healthier and stronger when I'm not in an unhealthy relationship. Being single and independent felt very good; so did entering a relationship with a sane and grounded non-alcoholic.
So I suggest asking yourself - what am I getting out of being in this relationship with a person who has problems of this magnitude? And are these benefits actually toxicity in disguise?