I hate having to rely purely on mushy or finer foods
Makes sense, but it seems that this is what you have to do until things start to improve. (It sounds like you would probably need more treatment than mestinon).
It is a bad idea to push yourself to chew, because you can end up having swallowing difficulties as well.
I had periods in which I couldn't eat or drink. The only way to get my required fluids and nutrition was by mixing a thickener into fruit juices and slowly eating them with a spoon with frequent rest periods during the entire day. I couldn't even swallow more than a few spoons in a row.
Speaking, chewing, swallowing and even breathing involve similar groups of muscles. When you are experiencing difficulties speaking don't eat. Rest a few hours before each meal (which means do as little physical activity as possible and avoid talking) and take your mestinon pill about 30 minutes prior to when you plan to eat.
There is a good chance that with proper treatment you will do much better within a few months. But, you do have to take it easy meanwhile so that things don't deteriorate. Take into account that myasthenia is an illness in which muscles become weaker with repeat use (the opposite of what happens to normal people whose muscles become stronger the more they do). That is why your can probably chew a few times, but then can't any more. That is why you have to put less efforts into the eating process and let your muscles rest and recover between each bite.
Take care and hope you do better soon,