Sounds like while you've had a year to "fix" the M, H has also (regardless of if he realizes it or not) had a year to "fix" himself. And it sounds like he's not doing a great job of that.
It's alot easier to blame our problems and unhappiness on other people, than to really, truly look at ourselves.
You've done the hard work. You're doing the hard work. H sounds unhappy with lots of things. Perhaps he thinks that by ending the M everything else will change. If Ss is the problem, once she's out of the picture, things will change, right? It'll all get better. (And I'm totally mind reading, so feel free to slap me if I'm getting out of bounds.) Funny thing is, he's been out how long? Doesn't sound like things are getting better with him. That might be where he's at. He's separated, (in his mind he may be on his way to divorce, we can only speculate) -- but things didn't get better for him? He's still unhappy, he's still upset about his weight, etc. So now what? And unfortunately, that's his issue. And I'd be tempted to say something along those lines, but you're in a situation where you can't because then you're back to the old Ss who is controlling, etc. But you know, sometimes people need to hear it. (Don't listen to me tho....I'm in the same boat. Look where speaking my mind has gotten me!)
Slight thread/post hijack -- you know H blamed me for everything under the sun when he left? Thought his life was going to be AMAZING once he got away from me. Truth is, once he got away from me, he got worse, and realized that I wasn't the source of all the problems in his life (unless he's blowing complete smoke up my ass). And I think he's stumped - because now it's like "Oh [censored], now what?"
Back to you: you know that you cannot fix this. In the current mindset H is in, it's his way or nothing. And that's on him. You can control your boundaries, and once the holidays are over (soon --- so soon!) hopefully your interactions can be less. And by all means, when it comes down to take the tree down -- tell him you'll need help putting the boxes away.
((Ss))
M:32,H 32 T:10, M5 BD/H Move Out: 9/2014 - extreme anger H Mental Illness Diagnosis: 4/15 Served D Papers: 10/15 Divorced: 11/15