The correct answers are I was so bored that I almost fell asleep in the theater. and The three-hour documentary was incredibly boring.

Use -ed adjectives (like bored) to describe how someone feels.

Use -ing adjectives (like boring) to describe the thing or person that causes the feeling.

A documentary cannot feel emotions, so it cannot be "bored." If you say "I was boring," it means you were making other people go to sleep!