Here's another photo of the split beak. In the second copy of it, I tried to trace along the edge of the split so you could see it. Sadly, my mouse is acting up and I'm out of batteries for it, so it's not a great drawing...
So today, we went on a trip to the avian vet, woohoo!
As gnarly as the beak split looks, it turns out he will be okay. The vet (who was amazing) said that although the bird knocked a chunk out -- which is why it looks so bad -- the beak wasn't all that overgrown, and will grow back out normally as long as it is trimmed down. He also said that it doesn't reach far enough along the lower beak to interfere with drinking.
He trimmed both the top beak and the lower beak. After he cut the beak with the nail clippers, he smoothed up the edges with a big emery board. He wants me to keep trimming both beaks until the lower beak grows out.