Sounds brilliant, Millipede. you sound very wise and clued up.
I particularly admire this insight:
"to do with the mounting resentment of the past 10 months. The less he's participated, the more I've stewed, and I think I've been shutting him out in my irritation. A case of "You're rubbish, I can do this all without you (and a good job too)" and then getting even more cross and confused that he doesn't do more. "
If you're going to break that dynamic, well done. My ex was extremely resistant to discussions about how he could do more and how broken I was, but even still, I regret not trying harder to push through that resistance, because I was broken and I did push him out as a result, and we did have a terrible relationship partly because I just had no energy for warmth, tolerance, openness, experimentation. Somehow, even if against his will, and for his own good, you must give him what he needs, not what he wants, or you're over - and that means he has to step up to a point where you can respect him; and the hard part, somehow you need to feel that he respects you (no idea how to get a man to respect you when he doesn't already, but I know I failed on that and it was partly to do with enabling him living in a cloud cuckoo land where he was an equal partner and I was just a feeble person who found easy things too hard - because the fights from my attempts to change that perception were too hard)
I really really think that marriages between two people sometimes really need to be broken open and exposed to other influences. I think that the privacy of a couple in a nuclear family can be very dangerous because once a man has lost respect for you, who can make him see you with different eyes?
Anyway, rambling now. you sound great. Good luck