You might explore our TOS forum and the sticky threads above it..
TOS can be a tricky one to get a clear dx.
Drs like clear cut tests or maging for proof, but some TOS can be soft tissue based.

Did any PT or DC try -
Top rib mobilisation
Manual trigger point release
Ultra sound
Low level laser
IFc stim

How is your upper body alignment?
Head forward, shoulders hunched or rolled forward?
Are shoulders, hips., Knees level across?
I hope pt and dc checked those. But just checking for sure . If not.. Seek better ones .

Many in the past had trouble being treated and diagnosed with TOS until they had increasing pain and symptoms that required rx meds or surgery..
I would call it pre TOS, a point where it can be turned around with expert treatment and self education , floow thru with self awareness.
It took me yrs but could have been less if not for work comp delays.

Even a long ago whiplash or shoulder, neck minor injury can cause issues as we age..

So there was a period of time when one of the doctors thought it was TOS . All mri, nerve testing, angiogram came back normal (but I know this doesn't mean anything). But after two rounds of scalene botox with zero improvement, the doctor said he couldn't diagnose me with TOS. Definitely tried physio and rmt for TOS (rib mobilization and all), but no improvement...