"I am seeing some slight improvement again so far, but I still wonder if my neck has anything to do with this. My therapist is also trained in Cranio Sacral Therapy, which does help get the knots out and loosen the muscles, but I still have a lot of pain at the base of my skull, in the suboccipital region, and my upper cervical spine feels "jammed" (I don't know how else to describe it). So I wonder if this is causing that last little bit of dizziness I was feeling a few months ago."

Keep the CST away from your skull. The upper neck work is good. Gentle.....

An upper cervical chiro may help. They each have different skills sets and every patient is different.

It is extremely important to be disciplined with head and neck posture, especially during sleep and rest. I know that I could be great one day then all messed up the next because of sleeping neck posture.

Anxiety/stress can sometimes cause neck muscle spams that could magnify your problems. Your relapse after the stressful event suggests anxiety may be making your symptoms worse, either just the anxiety or the anxiety causing muscle spams. Learning to remove yourself from stressful events when possible will be a big help.