I'm sorry if I'm sidetracking here but one of my kids had one heckuvatime writing at one point, too. For him, it was an issue of fine motor skills, but I can imagine there can be other delays/learning disabilities too that can have the same effect: It gets frustrating when you can't write as fast as you think. I'm sure you're all hooked up with support systems and therapists and stuff for his learning disability (you just seem to be "that" kind of mom, who digs till you find what he needs!) but if not, I know there's quite a few ideas out there on how to work through writing difficulties...
I'm in another place in my life than you are, but I can relate to the exhaustion. A friend of mine who went through an ugly ugly divorce said the first nine months, she did nothing but work and sleep. 10, 11, 12 hours a night, and still woke up tired. I've thought about her a lot in the past six months because that's been my life, too. I think sometimes we underestimate how exhausting emotional stress is on our bodies.
My go-to solution is always lowering my expectations of myself.
So my house may be a wreck and we may eat frozen pizza and cereal for a week and the kids may get to spend waaaaaay more time on their computers than I like them to... but sometimes, a mom's gotta do what a mom's gotta do. I hope you can get some rest!