When DS had a little friend at FDC who was biting him they used to put the boy in time out when he bit and ignore him for a few minutes. They had some other strategies too I will ask on Monday cause they worked.
Hugs to you hun, it must be very upsetting and stressful, my DS is a wild one and I have ended up in tears of embarrasment at him lately cause of the looks that people give you.