The classic game-jam crunch, I know it well. Though with the extra information that this is your first attempt at an non-fanfiction original work, really solid effort I must say. You probably picked up on it, but the crutch of fanfiction is the characters come pre-made, so when moving to an original work, you really have to build characters from the ground up. Same thing with having a direction that you want to take the story and making tough choices on which aspects might need to be cut or further fleshed out, especially mid-way through the drafting. Don't knock on your smut writing experience though, tap into it, especially the wildly inappropriate stuff (I loved the gag of Bryne's censored sex talk, but man if I could hear what he actually said). I agree though, I think you completed the assignment and this'll be something you'll learn from for your next project.