It seems like something definitely shifted but it can revert back with proper care. The TMJs are dependent on the neck and upper back. Not only are good posture habits important but your posture structurally is important and it takes time to modify. Massage, stretching and chiropractic are the best things I've done for my jaw and I've tried jaw PT and a mouth appliance. I've recovered from locked jaw and I'm 95% back to how I was before problems. You've really gotta put the focus largely on the upper back and neck. Facial and intra oral massage is good too, you can do these yourself. Upgrade your pillow to an adjustable cervical memory foam one like this:

https://www.amazon.com/dp/B0B3MB2R4Q?ref_=cm_sw_r_apann_dp_P22BCE4CJNT0GFEH387X

Do this stretch before bed, work up to 15 min: https://www.reddit.com/r/TMJ/comments/twkk5y/if_you_have_a_foam_roller_try_this_stretch/

Also I know it's hard but don't try to purposely mess with your jaw as far as maneuvering or doing anything tough on it. Treat it like a baby lol. You're right about TMJ specialists though, the people treating this disorder don't even fully understand it in my experience.