Hi Jennifer!
 
I have a shelter ferret that sounds very much like your biter.  I've tried
everything also...even biting her on the scruff!
 
The best thing that works on her is bitter apple.  I'll spray it on my
hands, arms or legs (whatever is exposed).  Of course, this can dry out
your skin.  I've heard mixed things about this, but sometimes I'll spray
it across her face.  That makes her leave me alone for a while.
 
Good luck!
Jeannette
[Posted in FML issue 2698]