In my opinion, any kind of "rules" about screenwriting should only ever be taken into consideration, at most. I think it's good to educate yourself of "formulas", patterns and structures that have worked well for others, but at the end of the day, you should just write the story however you see fit!
Not at all. But his approach does provide a useful guide to thinking about your story's structure. Movies would be boring if they all marched to the same drum beats.
It's important to realize that your characters need to grow as a result of the experience. To help with that, it is useful to provide both sides of the conflict-the protagonist's view and the antagonist's view. The resolution needs to resolve the emotional (subjective) story even if factual details (objective story) is left somewhat open.