nice to see you around, Nixon. i read through every page of Dave's recovery, shed a couple tears for you both, and seeing this type of abuse from the same owner Dave was rescued from is beyond infuriating.
if your friend is truly your friend, and they fully understand the animal abuse going on in their own home, they should be completely understanding of any actions you take with proper authorities. if this had been an animal with fur i can believe she would have called proper authorities herself.
i highly encourage you to take this route, and properly vet anyone you speak with on the conditions of Dave as well. i'd go so far as to show them your Dave thread; it's a real-time timeline of the abuse and extensive recovery. heck, i think i'd want to talk to someone in person (but i understand if that's not possible for you).
you're and incredibly smart, caring, and brave young person, Nixon. i know you can do right by these animals as well as have this person understand the repercussions of their neglect and abuse by having authorities show him what happens when you abuse an animal.
i wish you the best of luck.