Hi Starburst, Sorry to hear about the autonomic dysfunction progression.
Have you considered Rituximab ? Here it is given for RA.
I have some neurological problems, most of them autonomic and it is probably caused by an autoimmune disorder. I got Rituximab and it helped tremendously with the POTS (high HR when standing).
Maybe you could pay for the antibodies tests that your gastro recommended ? if they are positive would it be easier to justify more expensive treatment?