There is a product by Dr. Scholl's called Moleskin.

It comes in several types:
http://www.amazon.com/s/ref=nb_sb_ss...ch%2Caps%2C184

It may be able to pad the spots you are rubbing. With wearing them they tend to stretch out, so may do that for you and cause less constriction around your thumb.

My version is shorter than yours. The medical ones often are used for immobilization when casts are removed from wrist surgery. I find the heavy duty ones, rather overkill.

My brace is neoprene with lots of velco for adjustment, and still has the metal insert to keep the wrist straight. My only disadvantage with it is when it is hot out... they hold body heat, but in winter, they are actually nice.

I usually only wear them at night. I find any brace during the day intrusive. But when I was pregnant, I wore them 24/7 for over 2 months. (the neoprene ones were not available then, only the heavier sewn nylon type)..

Once you wear them a bit, you learn to hold your arms and hands in a straighter way, so the braces are less needed, except for at night.

I'd get one of these for your dominant hand, and see if it works and is more comfortable. You can always use it in the future.
I've worn out 4 styles in 30 yrs... and this one shows the least
wear so far. But I only wear them in bursts, when I have flares.