You're starting to go along the right lines of thinking, I don't want to add the other lines because they wouldn't work so well, but there should be more.
Two clues, first there is a VERY strict structure to how this riddle is written, no line is irrelevant or could be moved. Remember what I said, the reason I chose three FFs is not due to their plots, and line five was almost solved.
Another big clue is to pay attention to the exact wording of line two.