I don't know why you are getting such a hard time on here, or why everyone has decided your husband is some poor put upon man who has a right to be downright rude, make you feel you can't be yourself in your own home, you are creeping around at night trying to be quiet and not upset him. Weird, and I don't think typical of replies you would have received at another time point or perhaps on the relationship board.
You don't sound like a 'nightmare', that's how women who are expressive and don't just creep about often describe themselves, but nothing you write about here suggest you are exceptionally nasty, domineering, controlling-just a normal person, with normal moods, looking after several children and working hard.
Your husband has withdrawn, doesn't want to listen to you (and why is that ok even if he's listened for 20 years, if you stop listening and communicating with your partner, then your marriage will go down the tubes whatever the cause?) and isn't into you anymore.
I would stop flogging the dead horse of trying to find out why he's behaving like this, because it could be a) fed up after all these years b) someone else c) male menopause d) mid-life crisis e) thinks he has a right to be a grumpy old man.
Whatever your personality, and however bubbly/fun/highly strung you are, you used to have fun together, and now you don't and he doesn't even seem to like you. That's not nice and it's also not nice not to tell someone what's going on if you don't actually like them anymore, so even if his actions were 'justified' which I don't believe they are, he's still an emotional coward with his 'it's all fine, I still love you' stuff whilst snapping and getting angry to the point you can't be yourself in your own home.
I'd stop trying. I'd continue to have fun with the children, and look to a life outside, so step up any career plans, increase hobbies etc. I'd also wait til things are calm and have a very basic talk with him and not be fobbed off with his crap about loving you but treating you like you are very irritating. I would also think about leaving as it's very soul-destroying, however much you are to 'blame'. Don't spend time working that out though, you may never do, I'd look outside for your fun and happiness and perhaps adjust your thinking about whether a life outside this might work for you for the next twenty years.