I think that Miller is able to construct a domestic situation full of tension and discord to underscore Willy's failure in the personal realm, as well as in the professional realm. If Willy's family was happy and if he were to be a good father and husband, then he would have a realm into which he could retreat. At the same time, it would give him a sense of balance from a personal point of view. One of Miller's strongest elements of characterization is to show Willy as connecting to the modern individual in that he features a lack of balance. His instability comes from the fact that he has failed to achieve anything in his dreams or his ideal, something that is rooted in a lack of balance. For Willy, the presence of tension and discord in the family is reflective of yet again another realm in which he is a "zero." Miller's use of developing this in the characters of the family helps to substantiate these feelings within Willy, and feed the desire to commit suicide as a way of becoming "something." The use of tension and challenges within the family are ways in which Willy's character is developed. The construction of a subjective world where there is tension helps to illuminate the total scope of shortcoming that confronts Willy. Willy's own lack of reflection and rumination in this realm helps to substantiate this.
Throughout the play, Arthur Miller creates tension between the family members by illustrating their delusion, worry, and constant arguing. Happy and Biff continually disagree and fight as Happy portrays himself as an unreliable, habitual liar. Happy is more than willing to lie to his father and refuses to accept the reality of his situation. Linda is continually criticizing her sons for not supporting Willy and is worried about her husband's well-being. Biff cannot stand being around his father and tries his best to act amiably for his mother's sake. As was mentioned in the previous post, Miller's use of discord and tension reflect Willy Loman's failures both as a professional and father. Willy raised his boys to value appearance over substance and did not instill in them a sense of integrity. The tension between the characters also highlights Willy's unattainable expectations for his boys. They will never live up to their father's expectations and find it difficult to please Willy. Biff wishes to live in the country and work on a ranch but feels inadequate because he will not be paid enough. The problems that Biff, Happy, and Linda experience are directly linked to Willy Loman. Willy's delusional, pathetic character has created tension and discord for each member in his family.