I am a doctor of chiropractic with a specialty in extremity injuries/disorders, so this is right up my alley.
Good suggestion to raise/lower the strap length to put your bass at a different angle so as to reduce the bend of your wrist. Do that.
You're correct to lighten up on your touch and let the amp do the volume part. Smart.
Also, wear snug wrist braces on both wrists while loading your gear (no need to further strain your damaged tissues). Don't wear the wrist braces while playing (you'd play awkwardly).
Get treated by BOTH an acupuncturist and an advanced proficiency rated activator method chiropractor (try
www.activator.com, go to "find an activator doctor"). Only use an advanced proficiency rated Dr., as they have the training to fix wrists/arms/hands/fingers.

Dr2Kitties