That's a very good take on the duel between the three and Ariana's death. What I liked most was when Albus realised in mid duel that he loved Grindelwald. I also love how you described Gellert to be so cool after what happened: "He shook his head at the boy. “You’ll just make those wrists of yours worse.”"
Only complaint: The incantation for the Cruciatus Curse should be "Crucio".