I wouldn't worry, harpmom. Your bun sounds exactly like my rabbit was when I first brought her home. Like yours, she was a shelter bunny who had had a rough past (she was apparently abandoned in a parking lot and was almost eaten by a fox).

When I first brought her home she was quite vicious and not at all trusting of me. She frequently bit me as hard as she could, and barely tolerated being touched. But I persevered and she's mellowed quite a bit.

The most important thing is to have patience and be gentle so that the bun learns to trust you. It probably won't be an overnight process, but I've learned first hand that it is possible for angry bunnies to mellow out significantly