I'm not sure on keeping fancy goldfish with koi in a pond... I would have thought koi would be very fast for the fancy varieties.
Perhaps speak to the pond owner about you're concerns and ask how they're getting on
You could always look for someone in the local area who perhaps only keeps fancy goldfish
Perhaps look for a local fish keeping society they might be able to help?
As for the bronze goldfish's tail being bent... I believe sometimes fish can have scoliosis (bent spine) so it could possibly be that, not damage from another fish.
But well done for the rescue and all you've done for the fish so far