There are exercises one can do, but it's up to God.

It sounds like he blessed so far with a partial recovery and with a wife that cares. 

Search online for more. 
http://www.exploratorium.edu/snacks/proprioception/index.html
http://sportsmedicine.about.com/cs/conditioning/a/aa062200a.htm

 

I broke my neck at the age of 22, a C4-5 fracture.  I was initially quadriplegic.   I have regained much function and today I can ride a bike, cross country ski and play golf.   It took me about a year to regain full movement.  Today I still walk slowly and my balance isn't as good as it once was, but I would say yes, propreoception can come back.   I am now playing my guitar again.
I am 39 years post injury.   Check out my blog: www.RidingandWritingUtah.com to find out more about me.  

Yes, check out my facebook - Re-hab revisited I go through my process, I too a c4/5.