I'm not sqad either, sorry. But all of these symptoms could be caused by brain problems. The vomiting could be part of the anxiety and fits could indicate infection or damage in the brain. The obvious suspect as far as hallucinations go would be schizophrenia, but i assume all the obvious causes are being looked at already.
Have the healthteam given you any ideas so far?
Sqad does like a good history, so maybe you could say which mental illnesses his relatives have?
Must be heartbreaking. Lots of love to him xx