The straw that finally breaks the camel's back is when Suzy tells Victor about how his father went back into the burning house looking for him. Victor is then forced to acknowledge the fact that his father did love and care for him. Going into his father's wallet and seeing the picture of his family reinforces this. Victor then pulls out his knife and cuts his hair. Perhaps cutting his hair is symbolic of giving up his old notions and starting over.
Victor does make one last attempt at assimilating the new information.
On the drive home, Thomas tells how Victor's dad said that the only thing that Victor would ever be good at is Basketball. Perhaps Victor realizes the truth in this statement. He has been so busy playing the martyr and feeling sorry for himself, that he hasn't done much but play basketball. Or perhaps, he held on to basketball because it was something that he and his father shared. Victor becomes very angry and retaliates by firing back at Thomas about how his dad was a drunk and an abuser.