Couple of quick updates. First, my special diet (eat every three hours, small meals, no heavy carbs or salt) isn't heading off the attacks of weakness. Second, my aunt who suddenly came down with balance trouble and double vision has half a diagnosis from a neuro-ophthalmologist: Graves ophthalmology.
Graves disease runs rampant in that side of my family. Evidently Graves disease can cause double vision even in a patient whose thyroid isn't running hyper. The mechanism is that the tissue behind the eyes is just a really good fit for Graves antibodies, so they tend to collect there, and that causes double vision. The neuro-opth didn't see any signs of a myasthenic syndrome. Her balance troubles are resolved and still unexplained.
So...well, so I still don't know what's going on. I see the Boston neuro on Tuesday.