Aww Rumpled,
sorry I havnt got back to this site sooner, I forget where Ive posted messages!! Sounds like you are going through a fair bit at the moment, I whish I had some answers for you. If you dont feel comfortable with what the doctor has told you, (I now trust my instincts alot) I would go for a second opoion, after all whats the worst that could happen, you could find out what you may not want to hear, but will be able to start treatment. Is this doctor saying that he wants to start you on meds?
I didnt have a thymoma, and have had a thymectomy, it seems that mg is so very different for each person.
Yes I get very tired, but my neuro says thats not the mg!! I also have alot of arm and leg pain again, not apparently related to mg, so I just put up with it and go and rest when its bad.
If I havnt answered some questions you want answered feel free to ask, Im a bit brain foggy today.

Hope this helps a little
take care
redtail