The man continuously looking at the man while he is sleeping. This shows again and again.
I placed the boards so carefully, no eye, not even his could see the difference. He is saying that know one can tell that the boards were ripped up. If you rip up boards you cant tell unless you nail them back in.
The narrator is smiling at the police right after he committed a murder. If someone committed a murder they would be scared and overwhelmed. This is a character contradiction.