Hey Max,I also have read that GI physicians see a lot of people with LPR or GERD with TMJ - supporting the notion there could be some connection. Sounds like your dentist is on the right track. However, I do feel your surgery was justified so don't start to doubt that you did not need surgery.
Continue to be your own best advocate and if upper and lower splints don't work in a reasonable amount of time, consider seeing and oral surgeon for the TMJ issues.
Kindly,
Kitt