Sorry to hear about the ongoing chronic pain. Have you tried making/using a foot-mouse? I had some chronic wrist pains, and moused with my feet for a while. There's a learning curve to it, but ended up being rather efficient.
I’d considered it but I don’t really use the mouse much in the first place. I generally use a trackball (CST Laser) for big motions that I can’t do with keyboard shortcuts, and a Wacom tablet for anything that requires precision. And my ergonomic setup wouldn’t really accommodate a foot mouse either.