Will Oskar ever be able to come to terms with his Dad's death? Would he really have been happier if his Mom died instead?

Oskar will eventually come to terms with his father's death, although the grieving process is often long and difficult. As for the question f would he have been happier.....? No, I don't think so. Oskar's mother is absorbing his anger, and yes, she becomes not only the buffer, but the direct object of his anger. Her position is difficult but necessary. Grief takes any number of different forms..... Oskar willsimply need to work through it.