There is a very simple solution to this problem. Buy a second Yorkie!

Zoeybear used to go "berserk" biting, growling and acting like we were killing her when we tried to brush her. Now we have Baby Chloe. After I bathe Baby Chloe, Zoeybear crawls into my lap and waits to be brushed (and blown with the dryer) even tho' she hasn't had a bath. It's like she is jealous of the attention. Maybe try brushing a stuffed animal and ignoring your baby for a bit. Maybe he will get jealous like Zoeybear!