I don't know how advanced, or what kind of training / experience the PTs & DC had, or what kinds of therapies they used...
The wrong kind of PT can make you worse.

Also what may have brought on your TOS?
job/desk work/weightlifting/sports injury/previous whiplash- or any other injuries like that?

Even if mostly a posture/repetitive/soft tissue cause it can take years of rehab to turn it around.
And if you are still working while trying to rehab that will take even longer.

Therapies & tips -

Trigger point work

posture, posture , posture = the bad forward head/forward shoulders needs to be addresses if that might be an issue

diaphragmatic breathing - "belly" breathing

explore relaxation methods if you are stressed - stress = less oxygen to cells that need it & subconsciously tightened muscles

fluids = keeps the tissues lubricated so they don't get sticky - "sticky" fascia tissue can adhere to muscles, vascular & nerves and cause all sorts of problems

general nutrition for overall health


I could list more but it would be helpful to see all your sx listed for a better idea of what to suggest.