Your mestinon dose seems pretty low. I take 60 x 4 a day and 180 time span at night. I would contact your neuro about increasing the dose. The heat make everything worse. Have you tried staying out of the heat and in air conditioning for the day to see if your symptoms improve?

When my eye get really bad, I put an ice pack on it and get immediate improvement.

Reducing eye strain may help with the eye muscle weakness as well. Are you experiencing double vision?

thanks
kathie