I'm so sorry for all you and your son are going through. You mentioned Buhner. Do you have any of his books? He does suggest specific herbs for anger/rage. I have not tried all of them. I do take Gou-teng (Chinese cat's claw) that he says is crucial for neuroborreliosis. Kudzu root has been the most helpful for me for the brain inflammation and psych symptoms, but not everyone who's tried it notices benefit from it.
Honestly, the thing I thought of that may be your best hope as far as figuring out what to do for him is booking a consultation with Buhner's partner, Julie McIntyre. From what I understand, she has unique experience in working with patients much like your son. I know an old member who doesn't come here much anymore, rowingmom, consulted with Julie and found her to be helpful. Rowingmom's daughter's story of recovery is nothing short of miraculous and moves me to tears every time I read it.
Here's a link to her story./www.healingwell.com/community/default.aspx?f=30&m=3178304