Your son is so fortunate to have such loving and involved parents! What a great mom you are to do this for your son to help him! Just having that family support alone is going to make a huge difference for him in navigating this disease.
First of all, I'm very sorry your son has MG. It's not a pretty disease, and your son is showing signs of it progressing pretty quickly. I'm not going to sugar coat this. There is a lot to learn. If he doesn't take care of himself, he will end up in the hospital in what is called "crisis." Having just been there myself along with a few of my friends in the Facebook groups, it's not a fun time.
I would highly recommend he ask his neuro about IVIG. Some of us call it "MG Crack." It can really help to keep you stable without all the side effects and long term damages from the other drugs. It also works better in most instances.
Time released Mestinon is generally only used at night to help with breathing and swallowing of saliva. It releases inconsistent dosages and people have found it problematic during the day.
The symptoms your son is having are identical to my symptoms. It is critical that he rests when he has trouble with breathing, and when these symptoms are acting up. If he does not, he will likely get worse and end up in the hospital. I can tell you this will be the hardest part for him. I was an extremely active person and therapist, so my job consisted of a lot of talking and maintaining direct eye contact, and holding my head up straight, and writing. All things that are hard for an MGer. I can no longer work. I get too short of breath to converse with someone for a very long period of time. I avoid the phone at all costs, I rarely hold a phone conversation with anyone. I can't read out loud to my four year old. I don't want to scare you, but there is a fine line between not being informed and ending up in trouble.
There is no cure for MG, but there is treatment. The disease tends to progress in the first three years or so. I cannot stress enough how critical rest is, avoiding stress, avoiding heat, and not overdoing it. Those things can kill you. If you get too exhausted, your breathing muscles can quit and then you end up in the ICU on a ventilator if you make it in time.
Your son is on the brink of a very hard journey. His faith in God is what he needs to lean on the most right now. He will need to make adjustments to his work. He may need a microphone when preaching if he doesn't already use one so he doesn't have to exert his voice any more than necessary. He should sit down while preaching if he feels tired or weak! Take breaks when talking, mouth out the songs (that's what I do in church!) Don't schedule meetings or phone calls back to back, those breathing muscles must rest. When he feels short of breath, it's time to stop talking and go silent and rest.
Stay away from foods that are difficult to chew, like meats, grinders, etc. Think, rest the jaw.
Like 4 eyes said, this disease is NOT PRETTY. Your son is facing progressing of the disease. What started as ocular has very quickly become generalized. He needs to act fast and adapt or he will sink faster. Remember there is no cure; having had a thymectomy is pretty aggressive. I can't get my neuro to do one on me because I don't have a thymoma. I would push for IVIG if I were him.
I really can't stress enough that he has to make some fast adaptations or he will end up unable to work. He can't sing. It will exhaust his breathing muscles in no time. Maybe one song per service and that's it. If he has to choose between singing and preaching, what would he choose? If he has to choose between sitting during the service and ending up doing it from a wheelchair a year from now with a headrest, what would he choose?
God bless you and your family. If you are on Facebook there is a great deal of support there as well. There is a group I'm part of called "Myasthenia Gravis Won't Stop Me." I'm so sorry you have to deal with this. None of us enjoy this. If your son would ever like to talk, my email is email@example.com
. I'm a Christian, church is my only socialization, God is my savior, He will get your son through this!