Foxy-
If I could offer some of my experience and opinion... I suffered from extreme dizziness too. I did not find chiropractic helpful, and think that it is not an ideal treatment for concussion/neck injury. Especially if the chiro. does nothing to work on your muscles and soft tissues. I have found a very good neck PT to be most helpful, as well as a very good vestibular rehab. treatment center. If you are on the east coast, I can recommend one here where I live.
What I have found is that cervical subluxation is not the problem, but cervical instability is. My neck PT woks on strengthening my muscles to control my neck better and does gentle mobilizations to help as well. A very good vestibular rehab. center can help treat your other vestibular problems too.
Other things that help me... acupuncture, mindfulness meditation, moderate aerobic exercise, a very clean diet.
Of course, everyone is different

Best of luck on your continued journey!