Oh, the biting while nursing... I feel for you, it hurts... I've had to deal with this on/off. For a while, I believe it was mostly due to teething, as it went away on its own. The last 2-3 days though, out of the blue, she's found it funny to bite super hard a couple times (she has strong jaws now at 2years3months...), and see my face in agony... She bites so hard that trying to open her mouth with my finger doesn't work, but the trick I used is to gently pinch her nose closed, and she'll immediately open her mouth as she can't breathe... I end the nursing session right there an then after explaining to her that biting is not ok, and that it really hurts mommy. She's at an age where she understands it now.
When she was teething, and was also biting me and my DP for no apparent reason at times, I also told her that if she wanted to bite, she could bite a pillow instead, or the mattress, which she did a few times. I think it really felt good to her, so I really think she had a need to bite, but just didn't know what was appropriate to bite (ie no nipple or any bodypart...).