It is particularly relevant for Faber to choose the Book of Job for Montag, because like Job, Montag has lost everything. In the Book of Job, Satan inflicts upon Job a series of horrible experiences, ranging from boils on his skin to the loss of his entire family. The point is to test his faith in God. Job endures all his losses, with grief, but remains faithful.
Like Job, Montag endures great loss and although he is confused, he clings to the belief that books are important to living a meaningful life. Just like Job, who does not surrender his life or his hope, after losing everything, Montag continues to pursue the meaning of life.
Ah, good question! It is a commentary on, and a metaphor for, their current situation. That is to say, this society is suffering. Many things have been stripped from them; many trials have been set upon them. Each and everyone one of them has been suffering the trials of Job. That said, they need to remember that Job came through his trials a richer and still righteous many. It is a way of saying, have faith. We will get through this.