I haven't seen this mentioned before, so I'm mentioning it now. I hope I don't step on anyone's toes.

You need to keep a diary or journal of all that you have told us here. I have been told that if kept daily, a journal is considered a legal document and is admissable as evidence. Be sure to separate your feelings separate from observations and hearsay (gossip). You can write about your feelings, but the journal should be clear about what you are discussing. Make sure you credit quotes from people and give date, time, and location and any witnesses.

This would also be a good way to put each day in perspective and work through your feelings.

Get good pictures of any marks or excessive bites. I'm sure you are doing that anyway.

I don't know that you should mention this board. Yes, this is the same thing as talking with friends, but there are those that would differ in their opinion.

As a teacher I keep a journal of class events and meetings with principals. It has been a lifesaver. I let my bosses know I keep the journal, but I'm not sure you should let her know. You want to record her behavior without incentive to behave otherwise.

I think you are doing a good thing for Nathan. I hope you succeed in getting him back permanently.