tj21 -- I know this must be so difficult. And first, let me apologize that I have not read your other posts where you may have discussed some of the additional efforts you have going on. Since you already have a functional medicine practitioner who is leading the way, and as Chemar mentioned, there are so many factors that could be involved, I'll just share a couple of thoughts that may or may not be a fit.
It is possible with major immune issues to become hypersensitive to chemicals and allergens. I used to watch kids in the office of an environmental physician and saw a high pitched screeching tic triggered by formaldehyde exposure and a screaming tic triggered by mold exposure, etc. A food can also be behind it. Obviously you have a complex situation but do you think there are any environmental influences that may be playing a subtle role? For this, think in terms of an allergy to the nervous system--something doctors don't usually consider.