Wow. Just wow. I have pretty good vocabulary, but that is all I can come up with at the moment to sum up what I feel about your story. I thought it was, in short, amazing! I LOVED the plot, I LOVED the whole story, and I LOVED the fact that it was about the Joker. He is my absolute favorite villain. You should DEFENETLY continue! I have trouble writing long stories too, but I just think of all the possible paths the story could take, and follow the best one. Let me know if you need suggestions, but again, I LOVED it!