Biff informs Willy that he is leaving home forever, severing all ties with the family. Willy refuses to shake Biff's hand and tells him to "rot in hell if you leave this house!" Willy accuses Biff of wasting his life out of spite. Biff confronts Willy with the rubber hose and tells him he will not pity him if he commits suicide. Biff blames Willy for his inability to keep a steady job. According to Biff, the Lomans have not ever been truthful with one another or themselves. Biff is tired of fighting and blaming Willy for his own lack of success. Biff says that he and Willy are nothing but ordinary people who could easily be replaced by others. He and his father argue, and, when Biff breaks down and cries, holding onto Willy, Willy is amazed and "elevated" at Biff's love for him.
Scene 13 provides the final break between Willy and Biff. Both men struggle with their emotions and their inability to reconcile. Biff realizes in Scene 8 that he has been reinventing facts just like Willy. His realization is significant because once he verbalizes it to Willy, Linda, and Happy during Scene 13 he separates himself from them. Biff refuses to participate in the charade any longer. He chooses to accept himself on his own terms, not the way Willy imagines or desires him to be. His choice alienates him from Linda and Happy who are committed to maintaining Willy's fantasies at all costs. Biff is able to see beyond their shortsightedness because he realizes that denying reality is more dangerous and costly in the long run. This is exactly the trap Willy is caught in.
For Willy to admit that he is "a dime a dozen" is too painful. Such an admission would force him to openly contradict every grand story he has ever told or is planning to tell. Willy cannot deprive himself of his dreams by admitting he is only average. Even though he knows that he has failed his family, he cannot acknowledge such failure openly; instead, only Ben can share in this revelation. As a result, it is not surprising that Willy responds so dramatically to Biff's claim that their lives have been based on deception. To condemn Willy's fantasies is to threaten Willy's existence. Biff levels the final blow when he confronts Willy with the rubber hose. Not only does Biff force Willy to recognize the hose and his suicidal intention, but in so doing, Biff destroys Willy's dream that his suicide will redeem him.
spite a mean or evil feeling toward another, characterized by the inclination to hurt, humiliate, annoy, frustrate, and so on; ill will; malice.
blow [Informal] to brag; boast.
contemptuous full of contempt; scornful or disdainful.
dime a dozen an expression used to imply that something is available in large quantities. The fact that the item is not rare suggests that it is not of great value.
mutt a mixed-breed dog; an insult if applied to an individual.