Hmmm. Challenges, challenges. Mr. Highspeed is right--complacency is the enemy. It sneaks up so quietly and holds us so firmly it's hard to see a way out.
I wish I could send you some sleep :). I notice myself getting a lot less now that H is home, for many of the same reasons, and I'm dreading that my D5 is going to kindergarten in a few weeks--no more sleeping in with the kids for me. I don't handle things as well when I'm tired, and I don't like that. But I don't want to give up the late-night time together either. So no real solutions here for you. Have you discussed this with W? Would it be possible to make an adjustment in the daycare sitch to allow for a nap?
Are you still in the job you were planning on quitting this spring? If you hate it, definitely it's time to look for new opportunities, but that is much easier said than done when you are the bread-winner for the family I know. What do you really want to do?
Regarding W's frustration with her weight...I can say that I too have a more difficult time loving myself (and everyone else by default) when I feel unattractive--I become more self conscious, negative and critical in general. That's been one of the big discoveries in my journey. The whole GAL thing is vital to my well-being, and that includes lovingly taking care of myself, my body, my mind.
Since H has been home, I have made significant effort to continue my exercise habits, but I have noticed that being happy does make it easier to overeat, and I've lost the benefit of the stress diet. However, I do prefer to look healthy and fit to emaciated--there's a fine balance there. I understand your W has back problems--are there any exercise activities she might enjoy in your area such as water aerobics/swimming or yoga? Do you help with the cooking? Any chance you can quietly help in making more healthy food choices? Drink water instead of soda...those kids of things?
Sorry if there's a lot of unhelpful ideas here--I'll keep thinking on them and see if I can come up with more.
Best wishes--keep looking, the solutions will show themselves if you keep at it.
