Ditto to what Annie said about being on a Gluten-Free Diet. Even if he feels better, it is ESSENTIAL that he remain on a totally GF diet for the rest of his life. Researchers don't know what level of gluten will cause a problem in people with CD, and they don't know how long it takes for the intestinal lining to get back to normal after a "glutening".
If your husband doesn't follow a GF diet, his intestines will not be able to absorb everything that he takes in - that includes not only nutrients, but also medications. It can take up to 2 years for the intestinal lining to get back to full capacity.
Our youngest daughter's bloodwork numbers were back to an acceptable level after a year on a GF diet - she had numbers that were literally off the chart, and NO discernible symptoms prior to her diagnosis.
The "nasal congestion" that you are hearing is probably due to the MG - it is not uncommon to notice a nasal/flat sound in the speech pattern of a person with MG. Be sure and mention this to your husband's neurologist, because he/she will definitely want to know about it!
I hope that you are able to get things resolved with SSI - it seems to me that a sternly-worded, well-documented letter from your husband's doctor(s) should be enough to convince them of his inability to work.
I also hope that he is able to get all of the medical issues resolved soon - it's no fun to not be able to feel as good as possible. You be sure and take care of yourself, too - you won't be any help to your husband if you aren't at the top of your game.....