At 4-7 months, our Buster was t-r-o-u-b-l-e, trouble. We had all the same problems you're having, and now he's really, really good.
There's really not much you can do about the chewing and biting until he stops teething. The only thing you can really do is take away things that he's chewing on but isn't supposed to--that is, put him in an ex-pen if he's chewing on furniture; put your hands in your pocket if he's nipping at your hands; and put the potty pad in a holder like this one (
PetEdge: Clean Go Pet Puppy Pad Holder). Replace the no-no items with things he's supposed to chew on. Also, bully sticks are a great distraction for chewers.
If he's peeing everywhere in your house, he can't have access to the whole house. If there's one key to potty training a Yorkie, it's to give him space according to his potty training success--keep him in an ex-pen until he has no accidents there, then give him one room until he has no accidents in it, and so on. You're cultivating their instincts not to make a mess in their home by doing this.
The barking takes time, but most dogs do it for attention when they're penned up. Don't pay attention to him, and he'll learn that his barking doesn't work. Then he'll eventually stop. We had a stopwatch rule--10 minutes would have to elapse of no barking for him to be let out. Any barking, and the 10 minutes started over again.
Don't worry, we all go through this. Good luck!