Are Christopher's violent, anti-social tendencies and general lack of empathy for others a symptom of his autism? Or is it more the result of the emotional and physical abuse he has suffered throughout his life?
It's commonly believed that Christopher has Asperger Syndrome but he actually shows lots of signs of being much lower down on the spectrum such as wetting himself and acting years younger than his actual age a lot.
Darkness-Induced Audience Apathy: All of the characters are jerks in some way, even the main character, so some readers will struggle to care about anyone or how the book will end.
Nightmare Fuel: Christopher's dream. To be precise, it is about a virus that spreads through certain facial expressions, spreading like a computer virus, and leaving alive only people like Chris that never look at others' faces.
The real horror about this scene is that Christopher considers this a good dream. He is so isolated from other people that the thought of all the people he doesn't understand (and who don't understand him) dying and leaving him alone in a quiet and unintrusive world actually makes him feel happy.
And if you're an autist or just have a good imagination, the sensory overload experenced by Christopher in London Underground definitely qualifies (shown very effectively in West End production).
And later, his father. Even though he did kill Wellington, just look at the man; his wife leaves him, leaving him to take care of Christopher by himself. Later, Chris hates him for lying about Chris's mother, and doesn't talk to him for a long time, leaving his father to sit on the floor next to Chris's bedroom. This guy needs a hug for all he's been though.
However, he knows enough about Christopher to recognise the extremely restrained gestures of affection he occasionally gives, and to him it is clearly an in-universe Crowning Moment of Heartwarming when Christopher actually does acknowledge his presence after everything that's happened.