Who do you see for your RSD? Is it the same neuro that is evaluating the MG? I would ask him what is the cause of your symptoms. Is it dystrophy from the RSD or possible systemic RSD? If your symptoms progress I would ask for a repeat on the SFEMG.

My emg on my legs has been abnormal since the injury that started the RSD 30 years ago.

Some doctors try mestinon to see if it improves symptoms. Responsiveness to mestinon is used as an indication of MG in seronegative patients. Getting diagnosed with MG can be a long process. It took me 2 years. There are many others here that took even longer. There are some here being treated with MG treatments (mestinon, prednisone, IVIG) that still do not have an official MG diagnosis. MG is rare and most neuros have never seen it and will not commit to a diagnosis unless they are absolutely certain.
Hang in there
kathie