I feel bad for the boy because he is the scapegoat for the father. I think it was the monster that caused all the misfortune in the family unless that thing is symbolic of something else. I like how you left that plot thread up to interpretation.
Despite the subject matter the story drew me in, I realized that is one aspect of horror is when done well it can pull you into its thralls. Its something I learned when I made my own Horror game for a game jam and play through Pocket Mirror.