Firstly ajordan, I'm so very sorry you've had this experience
What a horrendous time you must be having.
My understanding is that it's best to attempt to repair damaged nerves within the first 12 months (why, I don't know - but that's what a girl on this board was told re. mental nerve damage). If you haven't yet done so, it would be worth emailing other nerve specialists and getting second, third, fourth opinions. Even though you say went to a specialist in that field, the surgery hasn't worked out - so you may as well get as many other opinions as possible now. You have nothing to lose. I assume you have all your medical notes to hand?
At present, your priority must be to address the damaged nerve - I am sure the gummy smile/bite issues can be corrected in due course. However, seeing Dr. Gunson should shed some light on the issue.
You may want to investigate the use of concentrated stem cells (NOT fat grafting) for nerve regeneration. Currently, this method is considered to be experimental - they do it in Europe, however. I know of someone who's had 9 rhinoplasties and severe nasal damage - they are going to Italy (Dr. Raffaini's PS partner) to have these injections.
I know it's a long shot, but hopefully that will give you some comfort. It's worth investigating, even if you don't end up doing anything.
Of course, there are cosmetic options (face lifting, implants, botox etc.) to improve facial symmetry after facial paralysis but understandably you must want to tackle the cause of the problem and quite rightly so.
May I ask which nerve was injured? Perhaps the pain has something to do with the trigeminal nerve? It looks like the marginal mandibular nerve branch on that side was affected.
As for your jaw surgeon - I would get all your medical files and hire an attorney (don't mention this to any doctor you're consulting with, though). It's incredible that he's acting like everything's OK when it clearly is not. Sadly, some doctors think they are 'God' and will lie in the face of obvious problems in order to save their own skin. He probably knows you'll be filing suit. Personally, I hope you sue the s**t out of him for his blatantly negligent surgery - sadly, you'll probably find you're not the only one in the queue.