I am learning emotional vocabulary.
I stuck a bit with two emotion terms, that in Russian refers to the same world.
Pulling from your definitions:
You are disappointed in a situation, or a person, if you hoped or expected a certain outcome that failed to come to pass.
You are disillusioned, on the other hand, if you believed something that turned out not to be true.
Disillusionment is a subset of disappointment, and conveys a deeper feeling.