Moby-Dick Questions Chs. 116-117: At the opening of ch. 116, the last whales are killed

At the opening of ch. 116, the last whales are killed, one of them by Ahab.  Given his obsession with finding Moby-Dick, why does he hunt down these whales?  What does Ahab make of the fact that the dying whales turn toward the sun?  What is Ahab’s own relationship with the sun (see for example ch. 36)?  How does Ahab’s soliloquy in the last three paragraphs of ch. 116 relate to Ishmael’s ruminations at the end of the “Try-Works,” ch. 96?  In ch. 117, “The Whale Watch,” Fedallah makes four prophecies to Ahab that, by literary convention, we accept as true.  What four things does he prophesize must happen before Ahab can die?  For those who have read Macbeth, do you see a deliberate intertext in these prophecies?  What is the effect of Fedallah’s prophecies on Ahab and his quest for the white whale?  How would you characterize Ahab’s relationship with Fedallah?