I'm really sorry to hear of all that's happened to you. Do you have any before pictures to use a reference point?
I'm not sure what to suggest because I know nothing about issues liked this because, like you said, they are extremely rare. My lower lip is slightly less mobile and sensitive since my surgery but it is really negligible but it took a few weeks to get to this point from being significantly numb and is obviously nothing compareed to what's happened to you which is why I don't have anything to suggest. Maybe corticosteroids?