So, how did your w/e with the kids go? It does sound like you are a great dad and putting your kids best interest first is always the way to go. Too bad your wife doesn't think so.
The messy house, things left undone - those things often happen to busy people who work and have young children (I've let things go before too) but it is also a sign of depression. Her priorities are clearly screwed up but not much you can do - it is all out of your control.
Selling your home and buying one less expensive is the not the worst thing. It happened to me and it was the one thing I fought hard not to do. Now that it was done (3 years ago), I can say it was all for the best. The children can adjust to it - kids move all the time as long as they know they will have their own space, input on decor etc.
I lost 40 lbs in the first 3 months after ex left. Enjoy this time - I managed to gain a lot of it back. I called it the Heartbreak Diet. No, this is NOT what you want. But we can't control what they do, we can only control ourselves.
Stay focussed, try to live just one day at a time - that is all we really have to do. Come here to vent. We are listening.