Much of the arm use symptoms sounds very familiar..
My symptoms like those were caused by a major overuse event - then my spasmed (like locked up) muscles pulled my collar bones up and they got stuck in the raised position..
Until a PT professor tried a top rib mobilization and they dropped down instantly.. the relief was instant for me..
No other PT or my chiro (who was quite good) had thought or tried the top rib mob.. and it was quite simple to do.. of course if your nerves are impinged & causing the problem a top rib mob may not help.. but could be worth a test if no one has tried it for you yet..

It is hard to know if the nerve is the cause of the tight muscles or it the spasmed muscles are affecting the nerve.

My muscles were not sensitive to touch or pressure at all , could be why PTs & Drs were baffled. After things got resolved I realized I had been in pain but it was more a constant dull burning, boring, fatigue type pain. Had a hard to describe buzzing, tingling internal muscles vibrations in my arms.. so they had no clue what to do with that..LOL

Can you hear a pulse like /whooshing sound in your head/ears?
I had that sound the whole time until my spasms were resolved..