I cannot really answer any of those, since I have only had mine since 2007, but at least you have a diagnosis. If I were you I would do anything that I can to start on IVIG - chances are high that it will help since it is autoimmune. If you don't start on some kind of immune therapy, it might keep progressing.
Did they try other things like steroids?

I am also a graphic designer and so far my hands aren't that bad, but my main fear is loosing use of my hands due to pain or motor problems.
Can't imagine the kind of pain you have in your hands that makes you unable to do the work. I suppose you tried neurontin and other nerve pain medication and it didn't help?

Good luck