How do I pad the extraordinary with the ordinary without it being boring?
You should not believe you are having the chore of padding a main interesting story.
You need to have two interesting stories. In fact, you should not be in the dilemma where you have a story which you wish to portray as a series of someone's dreams but looking for a 2nd story to fill in the blanks.
You are putting the cart before the horse. You are deciding to eat with chopsticks before you even know what you would be eating.
You should be in the dilemma of having two compelling stories you wish to intertwine but not knowing how to intertwine them, and then voila! You found that having one as a series of dreams is the solution.
Did Lewis Carroll decide first that he wanted to write a story about Alice passing thro a mirror, or did he have a sequel to Alice in Wonderland and faced the dilemma of how to avoid making the rabbit hole strategy look stale? And voila! He looked in the mirror and decided it was a great idea? Just speculating.
So, you have to get back to your drawing board, or thinking couch, to think of two sets of compelling messages you wish to indoctrinate your readers with, and you face the problem of how to intertwine them. How would you like your pair of compelling story lines:
Two messages that have completely different sets of morals. Each compellingly right in their own individual way but they are each other's evil when juxtaposed. You want to confuse the reader's self-worth and ruin their perky confidence in moral and ethical judgment.
Two parallel stories with similar messages, trying to tell the reader that no matter which side of the universe you live in, the same principle would run its natural course.
Two complementary stories each looking for a solution to their respective set of problems. You gradually let the reader discover they are actually each a solution to the other's problems. But they are separated by dimensional segregation and therefore, impossible for the two to come together. You tease the reader's intellect cheering for a way to bring the two stories to resolve each other.
Then you decide, hmmm, how do I intertwine them?