I'm a little more positive. Went out for an evening ride on Cowboy and there wasn't much head-shaking and no stomping at his face. I exchanged his fly mask for the one with ears, too. All of it seemed to help.
The other suggestion for this syndrome is night-time turnout and stall during the day. After our ride and a little grooming session, I released him to pasture and that's where he is now.
There is an issue--physical problems creating behavior problems and knowing which is which. Tonight he pulled back again when I approached him with a brush...a little brush. I had to saddle him in the round pen. I just couldn't let that be it and teach him that pulling back is okay. I figured I'd better head back to the trailer afterward and loose "tie" him (rope braided through the ring, but not tied) and present him with lots of goodies from the trailer. He was much better after a while. I sat and he stood and relaxed and we spent a good deal of time like that until he went half to sleep in the "tied" position.
I feel like I'm starting again with him in some ways, trying to figure our way as we go, but I saw a little bit of the old Cowboy tonight--not entirely back--but getting there, I hope.