I can only take Mestinon, unless I have another crisis. The other drugs are contraindicated for a lot of reasons. I have to manage with rest and common sense, plus my afternoon cup of coffee.

I've had steroids, as have my friends, Dad, lupus patients I've known, etc. And I am NOT confident about the Pred care he his having.
Twitching in his face/hands could be a number of things, such as an adrenal crisis, electrolyte imbalance, B12 deficiency, etc. It might also be that the Imuran and steroids have kicked in and he might be overdosing on Mestinon. Is it still there between doses of Mestinon?
I would highly recommend that you go see an internist/primary doctor to discuss all of this!!!
Annie