How very sad for those poor horses and the dog. You absolutely did the right thing - those animals can't speak for themselves and the guy is not doing them any favors locking them away if he can't afford to take proper care of them! It makes me so mad, but unfortunately, abuse happens. At least you care - hopefully the authorities will take control and there will be a good outcome to this story!
The information you report is not going to become public knowldege. You don't even have to give your name in SC - I know you are in NY, but these agencies work by the same rules - they cannot divulge any personal info whatsoever - it's the law.