How to Tell if a Character is Important

Taken from Million Dollar Outline:

• Viewpoint for the narrative
• Named
• Powerful enough to change the outcome of the story
• Shown as suffering extreme pain, especially emotional pain
• Extremely likable
• Shown as struggling to do the right thing

Essence vs Identity

Million Dollar Outlines quotes Michael Hauge as saying "he has never seen a movie or read a book that worked where "the question of the protagonist's identity" doesn't com up. In short, questions like 'Who am I?', 'What am I?', and 'Why am I this way?' are at the core of every great work."
From another source, I heard this note from a Hauge seminar: In the beginning of most successful films, you see the protagonist in his everyday Identity, just fitting in, going about their regular life. Wesley (Princess Bride) is a farm boy; Korben Dallas (Fifth Element is a cab driver; Thomas Anderson (Matrix) is a programmer; James Edwards (Men in Black) is a cop. And then something happens--they meet someone, or learn something, which speaks to his Essence. At that point, the protagonist has to make a decision: is he going to hide within his Identity, or show his Essence? The Identity is safe, but unfulfilled; the Essence is unsafe, but fulfilled.
What conflicts arise because the protagonist, or other characters, doubt him, and what must he do to prove he is worthy to hold the role he must take?