Is the title Moby-Dick or Moby Dick?

Moby Dick lives, at least in the novel, so I would also say he lives in the film. At the end of the book, Ahab has the chance to throw only one harpoon into Moby Dick, and it is the line from that...

No. He kills everyone, and Ishmael is the only survivor. But go read the book.

Ahab himself is the first to see the whale Moby-Dick near the end of the story.

A whale.

Chapter 80 is called "The Nut."