Poe dresses Fortunato as a fool because he followed Montressor into the catacombs in hopes of sampling a rare bottle of wine which are the actions of a fool. In the end he allows Montressor to manipulate him and kill him without realizing the real intentions of his "friend" until it is done
The prewrite is just planning out how you are going to layout your essay rather then actually writing the product, so you can compare it to the plans rather then building the house.
