In my opinion, he is a sociopath. This makes it almost impossible for most people to understand how he thinks or feels or what his motivation is in any way for almost for anything. What a damaged mind like has developed to become and do almost never makes any sense to a mind that hasn't been damaged. Even for people that have studied these types of minds and experienced being around them in person quite a bit, it is still quite hard just to remember to even try to think like them because it is so different than most people.  

With that being said, from my life experience of being with a sociopath who tricked me into believing they were a normal person for over a decade, this quacking doctor is doing the same. He is doing whatever he can to make life the most interesting at all costs even to the point of it causing harm to himself if that is what is necessary to keep the game going and keep it interesting and fun. He is just playing a game. This former plastic surgeon and now illegal eye doctor is a sociopath and all of life is just a game to him. His rules are obviously very different than our though. 

To me, he is thinking or feeling that it would not be fun to just kill the doctor? It would be over so soon. He probably thinks it's hilarious to think about if he will go to the fridge and choose the right food to eat or not. He'll probably be laughing about that one little trick for days, weeks, years, and decades to come. He'll probably store it in his memory bank and bring it up from time to time and laugh out loud for no reason. He probably enjoys quacking at him like it's a hilarious joke. Everything he can do to make it more fun and interesting and memorable to him, he will do it. Maybe he's burned enough people by setting them on fire at this point. Maybe it became too boring. Who knows? 

Sociopaths make absolutely no logical sense. He probably also gets a real kick out of having someone's life in his hands and then letting him go. He is a god now. He is all-powerful and was forgiving. So he is a kind and benevolent god. Now, I'm not saying any single bit of this makes any sense to any regular human being. They think almost exclusively in fallacies. So, there's my take on the good doctor. What do you think about my theory?