I'm saddened by your rough day and by the words of those dear sweet confused little ones. They'll understand in the end that you love them and did all you could for them and your family. There will be a day when they realize that they'd rather have a happy, healthy mommy than you trapped in a bad marriage just for the sake of having family around.
As for having someone to come home to and share the duties, I can completely understand. I only get my D on the weekends right now and because of that I have no time to do anything at all for me and work to get myself ahead. Now that I'm back in school, the weekend is my only real time to plan, grade, prep for teaching as well as do projects around the house here along w/ trying to GAL. I'm too spent at the end of each day to tackle these things, so I'm perpetually behind.
Like you, I wouldn't trade my baby for the world, but I do miss having someone there to share the load so we could both have our time to ourselves. Like you, I will have that chance to be w/ someone special again. This time it will be right...for both of us.
My D also told me I couldn't date b/c that would mean I'd get married. D said I couldn't date anyone but mommy. She said she told my STBX the same thing, so that is why I'm so concerned about STBX having her latest BF sleep over and be around D so much. It only confuses the little ones. I hope your STBX doesn't have his OW around your kids. They don't need more confusion.
Finally, I also agree w/ Ali in that maybe you should talk w/ STBX about spending more time w/ his children b/c they do love and miss him. He may not respond, but if you think your children would benefit from this, it wouldn't hurt for you to try to talk to him about it.
Don't worry, I remember he's a stubborn ass to talk to and you can get more deep, meaningful conversation out of the driveway sometimes, but it may be something to think about.
As for your D, take a look at her while she sleeps and I'll bet you'll see a lot of you in her. She sounds like a fighter...just like her mom.