I am sure your dog is fine. My brother got an American Staffordshire Terrier when he was in A&M Veterinarian School. He didn’t keep it very long because it showed vicious tendencies almost immediately.. He was not as fortunate as you are. He brought the dog to my house once and it had to stay in the utility room away from the kids, I never saw it again.
I've just been around enough dogs to know that there are big differences among the multiple breeds that are lumped into the generic term 'pit bull.'
If your brother had problems with an AST, it was probably because the dog was offended to affiliated with the Aggies and knew it wouldn't be buried in the endzone.