Hold the phone...he takes care of your children while INTOXICATED, he accuses you of calling him names, of not putting your entire self into the relationship, of overreacting (it's called blameshifting btw), and you feel that you have "got such a good thing going" ?
Can I gently point out that this situation doesn't seem to me like a "good thing"? Perhaps there's some wishful thinking at work here.
"Alcoholic" is only a dirty word in his mind, which is why he's supposedly insulted that you used that term to describe him. Perhaps he's feeling some amount of shame for his behaviour and doesn't like it when you shine the light of day on his dark grubby corners.
In any case, it doesn't matter if he's "an alcoholic" or a pink-spotted cow...the issue here is that you have a problem with his drinking. Yes? And he is unwilling to change his habits, yes? Also, nothing you can do or say will change his drinking...so it's now up to you to decide what YOU want to do.
I feel like some leech that goes around inflicting my standards on people who were perfectly happy the way they were.
This statement sounds like a reiteration of what he told you you were. There's absolutely nothing wrong with having boundaries and wanting them respected. This is part of a *normal* relationship. Be kind to yourself; you're being honest about what you want and he's just slamming you down because you are now refusing to play the role he scripted for you (the good girlfriend who keeps her mouth shut).
Finally, if he was so "perfectly happy" before you came along, then he can go on being "perfectly happy" all by his lonesome, now can't he?