I read some literature on this a while back and my takeaway was that surgery often doesn't work (and sometimes makes it worse), and most dentists and maxillofacial surgeons have no good answers. Of course, I didn't read everything ever. That was just my impression.

My medical approach if I had this issue:

My first exploration would be light physical therapy if there is any, inflammation reduction, and addressing what's irritating that area so much if possible. A mouth guard is a good start. Wearing your splint more often may actually help with that.

No gum chewing or other tough foods for a while. Probably forever, as joint problems tend to come back once you have them.

Periodically relax all the muscles in your upper body. Like you're melting into whatever you're sitting or laying on. Let your jaw completely relax. Your lips will probably part and you'll probably start feeling a tingling/vibration in your entire head as you travel down to the next, relaxing all muscles. I do this for neck pain and headaches and they've improved a lot.