This is all great advice. I've emailed his neuropsych about the dysgraphia, and I think a time limit on the homework is a good idea.
The dysgraphia seems to fit at least a little. His handwriting is bad, but he is pretty good at drawing. He doesn't seem to enjoy writing, but I'm not sure if he just finds it tedious (he seems to concentrate more on questioning the questions than just answering the question and moving on to the next). He constantly moves around in his seat, lays on the seat, rolls on the floor, and just seems to daydream as well. If I wasn't so worried about how this is going to play out as he gets older, it would be pretty comical.
As long as I can convince him to get to work and keep focus, then 40 minutes seems like a good limit.
I'm not really sure why his PS is low. He has childhood epilepsy, but I was not told specifically that it was causing it.
