The symptoms you mentioned below are what made me think of TOS or possibly RSI/myofascial related conditions. Just related to those symptoms, not everything..
Generic PT plans usually do not help for those with TOS..or complicated and mixed diagnoses for that matter....standard PT can make it worse...

[Within the last 4 days I now have numbness down the back of my arm and into my ring and pinky finger and weakness in my grip. It causes forearm pain and weakness doing things if I end up trying to use my arm. This is problematic since it is my dominant arm. I have been in physical therapy since June but I think my therapist is just overwhelmed and doesn't know how to handle someone with such extensive numbness and trouble engaging some of my muscles which leads to challenges with trying to strengthen in PT (especially weakness in lower abdomen, lower leg, balance).
I do have neck pain/base of skull pain occasionally, but it is not too bad and not debilitating.]
[It is now impacting my ability to use my arm it is scaring me because I do not want to lose the ability to do my job. ]