What did you learn about relationships when you were growing up?.
Did you see a heavily drinking parent too?. You, like so many others, are playing out the usual roles associated with such spouses; you are his provoker (because you never forget) along with being his codependent and enabler.
What are you getting out of this relationship now?.
I would suggest you make contact with Al-anon as they are very helpful to family members or people affected by another person's drinking.
Re your comment:-
"Most days I think, I can't do this, I don't want to do this and my life would be much calmer and happier without him. But we've been together a long time and we get on well - when he's sober"
Your life (and for that matter your DCs as well) would indeed be much calmer and happier without him. Your second sentence is the "sunken costs fallacy" and that causes good people like you to keep on making poor relationship decisions. People get bogged down by focusing on their sunk costs.
There are two ways to understand this process, both involving avoidance. One is an avoidance of disappointment or loss when something doesn’t work out. When a relationship doesn’t succeed, especially after a long period, especially after many shared experiences and especially after developing a hope that the relationship would be a good one, it is a loss. It is a loss of what might have been and an acknowledgement that a part of one’s life has been devoted to this endeavour.
Another angle to evaluate is that focus on “sunk cost” creates a distraction from one’s inner truth. The sentence often goes like, “I’ve already invested to much, so I can’t notice my thoughts and feelings that are telling me to end or change this relationship.” This is a type of insidious defense against noticing yourself. You enter into a neglectful relationship with yourself which divorces you from your inner thoughts and the quiet feelings that might guide you in your life. In other words, thinking about what already has been may prevent you from deciding what you want your life to be.
What do you want for yourself going forward?. How do you see the rest of your life playing out here with this man; an alcoholic who is self medicating his problems and life through alcohol. You do realise that alcohol itself is a depressant. I would also think that he is continuously also on a come down from alcohol so is infact never sober at all. He neither really wants your help or support; not that you are in any position yourself to be able to do that anyway.
You still have a choice here re him and you only need to give your own self permission to leave. You cannot rescue and or save him but you can indeed choose to save your own self from misery at the hands of his alcoholism.
Your own recovery from his alcoholism will only properly start when you and he are separated, until then it will not happen. You do not have to choose to ask people to help you cope with him (there are no coping strategies that work) and his attendant alcoholism. There are no guarantees when it comes to alcoholism; he could go onto lose everything and everyone around him and he could still choose to drink afterwards.