Welcome, Bearsmommy,
Your concerns are certainly justified, it seems to me. I don't have MG but did find this. That antibody test isn't always correct:
Myasthenia gravis - Diagnosis
- NHS
I do have MS, and your husband might have MS though it would be unusual for choking to be a first indication of it. Not unheard of though as just about anything can happen with MS.
It sounds as if he's been suffering for nearly a year now. I hope that some competent medical professionals will come up with some answers for you soon.