Thanks, Fly. Yes - he's relentlessly negative and when we were living together the way I responded to that (by taking it personally and trying to either fix his issues or convince him to look at them a different way) made both of us miserable. Non defensiveness and validating is really helping me here. I'm not sure it affects him one way or the other, but it certainly allows me to have a conversation with him without feeling like I'm being pulled into a black hole.
I don't want to tread on his life or get a rise out of him. My preference would be that he'd collaborate with me. But if he'd rather use our interactions to criticise me and bring up R stuff in order to blame me for it, I'm going to end those conversations and carry on with my life on my own. I won't exclude him from anything - he'll just be a guest, if he comes, rather than a co-host, because he wasn't offering to help, only to criticise, and I don't participate in that any more.
I don't feel sad today. I regret that he isn't offering what I want, but I feel it is more sane to accept the reality of that and go around it and do what I want, rather than hang about waiting at an empty cupboard, or blame the cupboard and cry about it being empty.