From what i've heard and experienced yorkies are stubborn when it comes to potty training ....and yes they do bark a lot..most of them. It is their nature to "protect" you. They don't need a lot of exersie but will probablly need to be let out potty more often as they have smaller bladders etc. If you want really good info on the breed read Yorkshire Terriers for Dummies. Good luck.
Also your cat...you have to be careful. Cats are a little mean sometimes and my parents cat clawed my Kelsey in the eye and it was bleeding everywhere. What a scary thing to witness! If I was you i'd declaw the cat's front paws if its an indoor cat...JMO