They get very, VERY frustrated at that age. DS hated anyone else talking to me and Dp (esp after DD was born) and used to sing "little Peter Rabbit" at the top of his voice.

DD1 was a shocking biter - so embarassing, but I used to look for the signs she might start up the chompers (stressful situations, too loud etc), and whip her out of the situation and into another room or something and distract her with a new toy. Maybe teach him how to hold his hand up and say NO! So he can "protect" himself if someone is in his face or whatever.