Few thoughts come to mind in case you haven’t already come across them yourself:

1. Unlikely but testing for sleep apnea, just to rule out since I’ve heard people with strange constellations of symptoms find improvement this way.

2. Testing for neurological autoimmunity - a paraneoplastic panel, neuronal antibody panel, anti-nmda receptor. There are a number of panels depending on the lab for these with some overlaps between them just check what they cover. These can be hard to obtain you need a doctor who groks them. Also can be expensive and sometimes difficult to have insurance cover but that’s usually helped if the doctor groks it.

3. A small fiber punch biopsy. (See Therapath for info, may also find a talk on YouTube called Small Fibers Big Problems by Dr Oaklander)

4. Investigate ME/CFS (probably already have) and dysautomomia (autonomic neuropathy, possibly indicated if biopsy positive).

5. I’ve just put my email in my bio. If you’re US based and want a recommendation for some helpful neurologists who can look for this stuff send me an email.