Sorry you are back in the hospital but it may be better for you with the breathing problems etc. VC and PF are not the indicators for resp. muscle weakness. PE, PI MAX, and MVV should be tested, also I cannot remember if you are on Mestinon but also pre and post Mestinon breathing test, MVV, PI, PE MAX can be tested.
Are you on any meds because that can alter the results of SFEMG and clinically weak muscles have to be tested.
I can send you the articles about this if you like.
I hope you get help, if not maybe they can transfer you to Hopkin's or get in touch with Dr. Penn.
Stay strong and I hope you get help soon.