Effect of repitition of "he would have" at end?

Oskar, his grandmother, and his grandfather all have one thing in common; they want to change the past. Oskar’s grandfather wishes he could have somehow saved Anna from her unfortunate death in the Dresden bombings. His grandmother wishes she could go back and actually live life, an experience she feels she has missed out on. Finally, Oskar wishes that he could go back to “the worst day” and either prevent his father from going to his meeting, or simply answering the phone when his father was leaving reassuring messages on the answering machine. Each character dwells on the past and blames themselves for the inevitable events of life.
Oskar unfairly blames himself for the outcome of “the worst day.” Knowing what happened, he wishes he could go back and change every event leading up to the attack on the World Trade Center. Ultimately his goal would be to keep his father safe so the family could continue living their lives contently. But if we could change incidents from the past that were important or life changing wouldn’t many of us want to? Oskar is being a typical human being in wanting to change the past. Everyone ponders the “What if” line every once in a while.
Had Oskar invented a real time machine to take him back to that dreadful day in September, he would know exactly what to do. He knows what his father’s routine was everyday before work. In his head, he has that whole day planned out…backwards. He has each small detail on rewind. “Dad would’ve gone backward through the turnstile, then swiped his Metrocard backward, then walked home backward as he read the New York Times from right to left (326).” In his head the process seems so easy. Why can’t he just close his eyes and press that gleaming rewind button that is so clear in his mind? It would rewind the tape labeled “The worst day” and everything would be normal again. But by the end of the novel Oskar has completed a transitional journey. His rewind button is not quite as clear as it once was.
Upon maturation, Oskar realizes that he can not change the past. Towards the beginning of the novel he may have reviewed every “would have” of that day and perhaps given himself a bruise out of frustration because it does seem so easy to change. But the effect of the “would haves” at the end is to show how Oskar has grown and matured. Although the past seems easy to change, he knows it is impossible. He is accepting his father’s death and learning to live with out him. His father would not want him to dwell on his death nor would he want him to blame himself for what happened. In the end he says “he would have”, but he accepts the fact that the past is the past and he must move on.