Without doing an exam it is hard to determine where the primary cause of pain is coming from. However, I will say that based on your history of carpal tunnel and thoracic outlet, your nerves are likely to be very sensitive. Not pinched, because not all pinched nerves hurt.
Many musicians benefit from movement therapy to help improve posture and efficiency of movement.
Better mechanics and better movement might just help you.
Dr. Christina Lasich, MD
I am a physical therapist. It sounds like you have more than just finger arthritis potentially impacting your function. I would recommend seeing a good orthopedic doctor who can help determine the cause of you pain.
You can also check out this website that has information about various hand and finger joint issues:
Hope this helps.