In older times, a hero was typiclaly one of noble birth blessed by the gods, choosen to do extraordinary things. Though remarkable, these skills are within his reach.
In modern times, a hero is usually (but not always) a person of humble or unassuming means who goes beyond the limits of his perceived abilities to accompish good for either himself, his famly and/or society.
The quotes you cite here are the attempts, though failed, of Willy to become a modern hero. He wants his life to have meaning and purpose. He does not want to be like the rind of a piece of fuit, who, once his purpose is used up, is thrown away.
The second is in relation to Willy's desire to live vicariously through his boys. He sees his own lack of success in women erased if Biff and Happy are successful in romancing.