I have experience with Demylenating autoimmune, is called MS. MS they say gets worse with heat, that just equates to it attacks the sweat glands... which could be called so many things, but hey call it MS. Theres so many variety of drugs approved for MS. So many symptoms: dizzy, mental, dysphagia, gut, neuropathy, all under the MS umbrella....
FyI, not a doctor, but maybe you could easily get a second diagnosis for MS with very little work... as MS is demylenation...

I have drug allergies. I can do copaxone and modified fodmap type diet. Copaxone has been extensively studied for myelin related stuff...
I also have to avoid meat (known enzyme missing for digestion which also relates to my drug allergies) so I have to take supplemental proteins to make up for it.
Wishing you better luck, sounds very rough , and not very fun