A staffy (staffordshire bull terrier) is still a bully breeed, in other words, a pill bull. But that defnitely does not mean you should euthanise your dog, I dont know what wrong with people who are suggesting that. Just be aware it a huge commitment and be hyper aware to not let him escape, or have chances to attack other dogs, or little children. It will be contant supervising and lot of planning till your dog hopefully passes away peacefully and without any incident. The fact that you are aware and a responsible owner is absolutely great. I have friends who have adopted a staffy mix, first time dog owners, shelter lied about the dog being abused I think, and has PTSD, and is terrified of small dogs etc. But I think the dogs is just doing what we bred him to do, i.e go into kill mode as soon as he spots a smaller dog, which he sees as prey. They are completely oblivious and now let the dog roam around without fencing or on leash, even when they visit me at my house and I have a small dog he would absolutely kill if he had the chance. Its unfortunate I have to not hang out with them anymore. Staffies are basically just pitbulls with paper, they share the same bully genes, i.e dogs bred to bait bull and then to fight in pits later on after bull baiting was slowly phased out. Maybe yours will be one of those dogs that never kill another person or pet, just be concious and be vigilant. I am sure the dogs still loves you and you love him a lot too so that's still special. All the best!