Dave, I thought an analogy might help understand Mestinon better.
What if you had a raging headache and a minor backache? You take acetaminophen but it only helps get rid of the backache and not the headache. You can't take more meds because, well, it's not good for you!

You would need a different medication in place of or in addition to it.
It's the same with Mestinon. If you take 60 mg., for example only, it may help with your leg and arm weakness but not get rid of the ocular/facial muscle weakness (since that may be worse). But if you take too much Mestinon, targeting the muscles that are most weak, your less weak muscles can become weaker due to overdosing.
I am on 90 mg. every three hours, round the clock. I can't take other drugs so that is why I have been dosed this way. A consistent dose for me 24/7 works the best. My eyelid/eyebrow drooping is very activity dependent or dependent upon things like stress, eye strain, driving, heat, etc. Unfortunately, those eye muscles tend to droop first. So if that's the one thing that is interfering with your daily routine, you may need to at least talk to your neurologist or a neuro-ophthalmologist about alternatives.
Pred does help some people but it does come with very serious side effects. Pred is a LONG TERM drug and is very hard to get off of. IVIG might work for you. It is a trial and error kind of thing. And there is almost nothing, besides remission, that gets rid of the weakness altogether.
I don't have any answers for you. Everyone with MG is different, like everyone here says. I hope you find a balance that works for you.
Annie