are biff plans about oliver realistic if yes why

I think Biff knows he is going to fail and his motivations for meeting Oliver are suspect. While Biff may have started to fail in order to spite his father, by this point his self-destructive behavior is ingrained. His plan to ask Bill Oliver for money was dubious at best, but Biff made it even more unlikely by pseudo-accidentally pocketing his fountain pen. In contrast to Happy, Biff does show some concern for his father's feelings; he worries that Willy will think that Biff intentionally botched the meeting with Bill Oliver.