1. simply view the photo you want to delete and if admin hit the move delete link and then delete it or edit photo and under there will also be the delete box.
2. If you set in admin for the user post counts to update the forum post count the post count on the forum will go up by one when someone uploads a photo or comments on a photo but if you run a recount posts on the forum maintenance it will 0 out anything photopost added.
3. No not really within the program. You can as admin edit one photo at a time and change the owner but no mass change. You would have to do that by query.