[alaskayorkie]

I think you've gotten some good advice here, but you're right to take it seriously. Eddie, my oldest, left the litter too soon also, and he's struggled with knowing how to play. I think bringing him around other dogs and socializing is a good place to start. Obedience classes will help with that. Also, let lots of people pet him and play with him.

Here's what I think is most important:
* Exercise. Dogs who develop bad habits are often bored and under-exercised.
* Barking. Put some pennies in a can and shake it when he barks.
* Outside walks. Distract him with games. Toss a ball. Have him do sits and reward with treats. Get him to focus on you and not all the scary things in the environment. If you pass something that sets him off, ignore it. If he sees that you're not concerned, he'll learn he doesn't have to worry about it either.

Good luck! Sounds like you've got a terrific Yorkie with a great personality.