Abby,
This sounds like the early stages of my life when I first found out I had a problem. The only reason they (neurologists) found out it was a form of MG was because Mestinon was making me stronger. And for the first five years I tested (as you seem to be doing) through trial and error the effects of mestinon, its side effects and advantages. About 10 years later I am actually taking 60 mg of mestinon 20-25 times a day (yes that is no a typo). Mestinon is absorbed by the body differently by different individuals therefore where some one might just need one or two pills a day I need 25. It is a huge difference in terms of my strength. My neurologist gave me the green light to test how much my body could absorb without causing crashes and I believe that you should talk to your neuro about perhaps experimenting. I am not a candidate for the prednisone which actually made me much weaker when I first tried it, so as I said MG affects everyone differently. But it sounds like you are on a good path because for me it has been trial and error and trying to figure out what works for you. The doctors will only know what you tell them and that's why sometimes their ideas may seem unimaginative or even unproductive.