GeneralWhat are the main differences between the movie and the book?

How do I understand the movie?CharactersProtagonist (Edward Norton):

What is the name of the protagonist?
What is the reason for his Dissociative identity disorder?
Why is he going to the support group?
Who is Jack?Tyler Durden (Brad Pitt):

What is the first time that Tyler Durden appears?
How many jobs does Tyler have?Marla Singer (Helena Bonham Carter):

Why is Marla going to Support groups?