I understand your frustration over this situation. But many people deal with this same thing every day. Insurance companies will do anything they can to not pay for services, so this is nothing new. Have you asked for the LRP4 test? The same company does that as the MuSK.
The more important issue here is that you don't know what is wrong with you. I have no idea how to help you in that regard. I wish I did.
I hope you can find a way to put all of this behind you. Stress is not good for the body. Anger only hurts you. You deserve to be healed from all you have been through.
Annie