6 month old crown hurts to chew on and feels off and causes TMJ tension. What should I do?

There are many factors: the material used, the cement used, the hydration (or "wetness" of the tooth at the moment of cementation), the bite....  After 3 adjustments, I personally would be remaking the crown or doing root canal therapy.  Not all nerve tests are the same (and if a tooth is in the PROCESS of dying, it may give misleading results).  Perhaps see an endodontist to evaluate.

I would recommend root canal therapy and would send you to a specialist, an endodontist, to do the procedure prior to making you a new crown.