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Whoa. Frankly his condition as you describe ("disorientation, passing out for a few minutes at a time, no balance, slurred speech, etc") as well as his other difficulties sounds extremely serious.
For more support and information about PCS, please also check out the
Traumatic Brain Injury & Post Concussion Syndrome Forum
It also sounds as if he needs some professional help for his past trauma that you mention.
There can be many reasons for head pain or head ache after TBI. He needs to see someone who is knowledgeable. Ask for advice on TBI/PCS forum and give your general area as well. Also, there are numerous, excellent brain injury Associations in the US for both the injured and their families and caregivers. This link is one of many ...
http://www.biausa.org/state-affiliates.htm