Do you think there's a link between intracranial hypertension, years of pain, untreated, and now functional neurological disorder along side the organic condition of iih? worsening quadparesis without clear cause?

Not feasible to pinpoint underlying relationships based upon your post, but clearly with a "worsening quadriparesis", with history of pain and intracranial hypertension, it is imperative to have the entire picture fully re-evaluated. Suggest a visit to a major university school of medicine and have this precisely diagnosed and treated as appropriate.