The Question and Answer section for The Curious Incident of the Dog in the Night-time is a great resource to ask questions, find answers, and discuss the novel.
In Chapter Nineteen, Christopher explains why he has numbered his chapters in prime numbers: it is significant that he has chosen a pattern for his story which, as he explains, is the pattern left when all other patterns are taken away. It is...
Christopher doesn't realize that his father is angry because he is speaking so quietly...... there is no hint of anger in his voice.
You are correct. Chris is on the autistic spectrum meaning new situations, especially social situations, scare him. He does not interpret social and environmental cues in the same way as non-autistic people do. Chris finds comfort in repetition.