Have they ruled out BPPV? Cervical vertigo? Has anyone said this is a cerebellar issue? I sympathize with the wild goose chase and the frustration in getting answers. If you do find something out, let us know.

I think that vestibular migraine may be the diagnosis of exclusion and we may be told that when there is no other answer. To me, that means they are simply saying the origin of the dizziness is the brain- not the inner or middle ear, not ear crystals, not the neck.

Nystagmus itself causes dizziness so I would also wonder the source of yours. Mine was an autoimmune reaction to cancer. Of course dislodged ear crystals can cause nystagmus and I assume you have done exercises for that (BPPV).