"I just want to be able to do things like snowboard, or ride roller coasters, or drive without feeling the bumps in the road, run, jump, headbang at a concert etc."

Give up on ever head banging. That is very dangerous. It disrupts the fluid flow and control in the brain and can cause life threatening damage.

Head banging IS NOT NORMAL BEHAVIOR.

Riding roller coasters will require learning how to ride them so the vibrations and quick movements are moderated.

Think of it this way. You made bad choices with BJJ. You cannot undo those choices.

I bet your PT and others are over stressing your neck. You need strengthening with minimal movement. Expect it to take up to TWO years to stabilize your neck if you are disciplined. You need to learn new movement disciplines.

STOP WHINING. That only makes improving more difficult. It stimulates the wrong chemicals in the body.

From past experience, most in your situation need a short period of medication. An SSRI, SNRI, or such. Some use natural supplements like 5-HTP and L-Theanine.