I think you should consider the wrist....it can refer up the arm.

If the towels don't work, I'd get some wrist splits which are in most stores that carry HBAs (like WalMart or Target) or pharmacies.

Keeping the wrist in an open position, can do alot. Eventually you can go without like I do... I've learned how to hold my hands while typing, using the mouse, etc and at night I put my hands on a pillow next to me. Back in the days of 80% loss of function for me, I wore them 24/7. But now only when digging outside alot, or doing some stressful thing. If they don't go numb on the steering wheel, I know I am doing well.

The typical tests for glucose don't show everything. Next time you get blood work, get, fasting INSULIN. If elevated, then you know this is going to be your problem. This happens long before fasting glucose goes up.
Also get a B12 test, (get your numbers from the doctor, because they use antiquated lab ranges), and a Vitamin D, since you live in the North. Low Vit D alone may be one player in your symptoms!