WELCOME TO YOU Erin & Cooper. He is so cute
!! What a lucky boy that he found you and you've taken such good care of him. If I saw him on the street I'd call him a pit bull dog also. I hope you don't live in Miami-Dade County.
Also since you got Cooper so young you might want to read about socializing him with other dogs, because those couple weeks between 6-8 weeks are a critical period when dogs learn how to play, etc. properly. Maybe you can find a good, POSITIVE puppy class to take him to.