Here is what I would do, in this order:
1. Fully assess him physically so you can create a prioritized treatment plan, as well as getting and understanding of what other tools/disciplines he might need.
2. Make sure he is doing all the foundational HLC principles
3. I would refer him to a NUCCA chiro instead, as with any head trauma you will always see and atlas Subluxation. This can create nervous system stress and musculoskeletal dysfunction.
4. I would find a skilled NMT to do work on his anterior cervical spine muscles. I have found that most people with head traumas do have a FHP, but the C-spine is straight (done through xrays). Releasing these muscles will facilitate alignment and healing.
5. I would find a skilled NMT that can do cranial and TMJ work OR a craniosacral therapist in order to realign his cranial plates
6. I have been studying the work of Yanda, Lewitt and Voijta through a system called DNS according to Kolar. It is a great system of tapping intot he CNS to rewire it without volitional movements. Go to this link on my site (http://www.eastwesthealing.com/resources_dns.html) to learn more and maybe find someone in your area that does it. There are not many, but there might be someone in your area that does.