Here is daisy18216's pit bull! (what's his name?) He is totally ADORABLE!!
With multiple male dogs, and especially with a pit bull - they should be neutered. This can help a bit with aggression, and keeping intact males together is asking for trouble. There is no reason for your dogs to be intact.
Again I reiterate - do not leave your pit bull alone with your other dog when you are not there. EVER. Yes, I understand that your dog gets along with other dogs - NOW.
As for signs of aggression...bumping other dogs with the shoulder, staring, growling, high raised head and tail, putting neck on top of the neck of another dog.
With pit bulls, there may be NO signs of aggression - just a sudden and very serious attack.
My dog is 3 years old. She went to and passed obedience school - and yes I had trouble with her pulling on the leash. This is characteristic of the breed and now she is pretty good, but still has lapses.
Here is a link which contains some of the best info on pit bulls on the net. I'm sure it'll be helpful!
the Real Pit Bull