I posted this same question about a week ago. LOL. Tobie is my first Yorkie too so I have had a ton of questions. From everything I was told, Yorkie's love to jump off of things and Tobie is no exception. He doesn't just jump.. he does a flying leap. Anyway, I was told that there are people who have had their Yorkies break a leg from jumping off furniture so you probably want to stop him if you can. I know it's hard... there is no way I could keep Tobie from never jumping off the furniture. I seriously thinks he enjoys it! I have been trying to stop him though when I think he's about to do it.
Oh, I forgot to add... as far as the weight I have no idea. I have heard that the weight usually doubles from what it is at 12 weeks (I think thats right) but I also know that just because thats the "norm" doesn't mean there is definitely something wrong with your baby. Hopefully someone else will be more helpful with this