I can't see your images, the links don't seem to work.
Without being able to see the images, I would say drag the shutter:
Use a slow shutter speed and a moderate ISO to expose for the costume's lights, then use a little bit of fill flash to get crisp detail in the rest of the costume.
Usually, random ISO noise doesn't bother me much, but the banding that happens in H2 (and even H1) are pretty distracting. I'll happily go up to 25600 on the 5D3, as long as I can get a perfect exposure with that ISO; when you're hitting those limits, there's no room to push it up or down in post.