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!

I did mention desk & office work:)

The forward head/shoulder postures of leaning forward to read books or papers at a desk can be a contributor.
This can slowly strain the neck over time, as well as closes the brachial plexus area where the nerves and blood flow to the arm & hands.
You would eventually start having some upper back and neck pain or discomfort if this is the case.

Some general thoughts...things be be aware of -
Do you tend to lean to one side or the other at the desk or often lean on one arm or the other?
shoulders uneven when looking in a mirror - one side dropped or raised?

If any of those posture things fit, being more aware and addressing those issues/habits might make your hand /arm symptoms lessen.

One quick thing you can try at night to see if there is improvement is this:

Have a snack before bed with protein in it. A protein type health bar like Zone Perfect with modest carbs (balanced carbs) will keep your blood sugar from dipping low in the middle of the night. Low blood sugar spells may cause numbness that goes away when you eat. Things like Clif bars have too much sugar.
A high carb snack may make the numbness WORSE.

Another thing to try is an NSAID like Aleve before bedtime. This will block inflammation, and tell you if your nerve issues are inflammatory. If it works to block your numbness you have a direction to follow with that.

cervical problems
 

I have similar problems from cervical disc. Hands and arms go to sleep or i get strong pain sensations that go down the arm into the palm of my hands.

amatriptyline has helped the nerve pain.

hi i am 19 year old male with pinched nerves in elbows too.

get sleeves for arms that wont let u move them at night, and tingling should slowly decrease.

if it doesn't call a neuro, when i pass out somenights i bend them and wake up with them asleep