Welcome to YorkieTalk and congrats on your new pup Charlie.
Yorkie nails are typically black. That is part of what makes trimming them without hitting the quick difficult. The white is usually the quick. Start working with your pup regularly on nail trimming so that he will grow accustomed to it. If the nails hit the floor and make a clicking sound, they are too long.
If his teeth are not all the way in, I believe he is younger than 12 weeks. Maybe a breeder or more experienced person will correct me. Max had his full teeth when he was 12-13 weeks.
The growth you indicated sounds normal. Puppies grow very rapidly. One formula for guessing adult size is to double the weight at 12 weeks. This is not a guarantee, but may give you some idea.
Post some pictures of your new little guy and members here may be able to give you some insight on his age. There is a fairly significant difference between 8-12 weeks.
If you have not already, be sure to take him to the vet for a wellness exam and to get him up to date on vaccinations. It's always good to establish a relationship with a vet's office too.