the way you just described your weakness, does sounds a lot like mine did as well. I think you may need to see a different neuro, one that is very familiar with MG.
I'm thinking that you may need to see a Neuro Muscular specialist.
I'm so sorry you are going through this!
Hopefully soon you get in to see another neuro soon, and get some relief soon through some meds.
I'd be riding my bike, and pushing the peddles would slowly get harder and harder, to the point I'd have to concentrate all my energy to my legs, just to get back home. Other times, they just wouldn't move. I know this is a scary time for you. Stairs are the worst for me as well.
best of wishes
Love Lizzie