I had the same surgery your father had, although a bone from my leg was used to replace my left lower jaw. It's a tough experience to come to terms with, especially the fact that it does change your looks and the way you "feel". I think your Dad is stuck in the process of grieving for his pre-cancer self, what he was before cancer and his life before cancer. It's such an easy thing to do to ourselves. I wonder if he has cried over this? I literally "said good-bye" to who I was before cancer. I'm not the same person and even though I miss her and feel like I experienced a death in my life.............the new me is living it up and making due with what the good Lord wants me to have. If he can get past that grieving process he will start to heal emotionally.
Good luck with it all.
Minnie