I would be concerned about combining CST and NUCCA. The CST can possibly undo the NUCCA.

What is the CST Therapist doing specifically ? Is it an osteopath doing the CST or someone else ? Most CST protocols have been replaced with Osteopathic Manipulative Therapy. Most OMT therapists do not do any cranial therapy.

What is IMS ?

What the doc likely means by needing to treat the mental portion is the anxiety from PTSD or otherwise can slow or prevent healing from the concussion. They can each make the other worse. Studies show that serious PTSD can cause physiological changes in the brain that are difficult to correct except over long periods of time. The more common anxieties that accompany concussions are simpler to treat.

My best to you.