Lily - I know. I have no idea how to make that happen.
Whether we stay together or separate, attitudes of righteous indignation, or blame, or resentment will be completely useless - in terms of communication, that's historically the block. Everything turns into "but YOU did THIS to ME!" - and the conversation is over. (even if not angry or acrimonious, P will not - will physically not - hear about things that he does that negatively impact me - he will cause all kinds of upset in the name of stopping that conversation)
If we separate, I have no interest (ok, very little interest) in trying to make him understand how his behaviour has negatively impacted me over the years. So if he disagrees that we need to separate, it will be a difficult conversation because how do you answer "why?" - everything isn't fine, but how can I say that in a way that is possible for him to hear?
If we do not separate, thing have to change. Again - how can I say what things, in a way that would be possible for him to hear?
I know he may well think that I have to change too. If I were interested in staying together, I would be interested in hearing what isn't working for him, or what I could do about it, but I would not be interested in framing the whole thing as being about me being a difficult terrible person. Which is what he does. And if I agree to a, b, c, d, e, f, that is wrong with me - thinking that we can work through his list first, so that eventually we can get to w, x, y, z and I can say things I would like him not to do, or do differently - it doesn't work, because my accepting a, b, etc has only justified him in his view that everything is about me being a bit shit