Reddit mentions of The K-9 Center K-9 Break Stick

You now know not to put your dog near any other dog, to your sorrow and the unfortunateness of all involved.

If you know you can't handle this dog, his behaviors and his energy level, then there IS no shame in giving him up. Not every dog is suited for every household and it seems you and your situation is best suited to a lower energy and more affable pooch. Not everyone can handle a high energy and dog aggressive dog, this also is not shameful! Your pet may be happier and healthier and safer in someone else's hands, meanwhile there is the actual perfect rescue dog for you waiting out there.

If you choose to turn him over to a shelter, be clear with his record against other dogs or they might make some stupid mistakes themselves.

If you choose to keep your dog, look into getting a break stick immediately, learn how to use it, and begin muzzle training. Get a no-pull harness or head-halter to curb his bad leash manners. https://www.amazon.com/The-K-9-Center-Break-Stick/dp/B004RU81VY

The only sure way of breaking them off each other is with a breaking stick. The finger in the butt is a myth that was told as a joke to see if people would try it. Contrary to popular belief pit bulls can’t “lock” their jaws with some special mechanisms that they have.
A breaking stick is a hard plastic polymer stick about 12 inches long very thin but about 2 1/2 inches wide. The tip is inserted into the dogs mouth where there’s a natural gap between their molars and then twisted which opens their mouth enough to put the other dog loose. Always straddle the dog and lock your legs around where their belly ends and hips begin to help immobilize them hold the collar with one hand and breaking stick with your other hand then break them apart.
It takes two people to break up two dogs that are determined to get each other. If you only break one loose the other is gonna hold on for dear life and probably start pulling and shaking too.

Source: I own game bred pit bulls for catch dogs on wild boar and occasionally they’ll lock up with each other.

Here is a wooden breaking stick from Amazon https://www.amazon.com/The-K-9-Center-Break-Stick/dp/B004RU81VY
I prefer the plastic. They’re much tougher and don’t splinter.

Dog aggression actually manifests with social maturity, generally (2-3 years). Around that age you'll typically see dramatic reductions in tolerance to foolishness, even with dogs that are good with other dogs.

Many pits will be dog-selective (or even dog-friendly!) up to that point, then genetic influence sets in and dog aggression will take hold.

My advice is to muzzle train and keep her away from other dogs.

Dog aggression and human aggression area entirely distinct issues, just so you know. Her dog aggression has pretty much no implications for aggression toward humans, EXCEPT with regard to "redirected aggression" in dog fights.

That is, even though she loves people, it is still a very real risk that any human sticking their hand in to stop her from biting another dog will get bitten. This is an excellent reason to muzzle train her, as well as invest in a break stick just in case.

At the risk of sounding like an asshole, you probably need to put a muzzle on your dog when you walk him anywhere there might be cats. You should also make sure you carry a break stick with you and know how to use it just in case your dog gets a hold of something and decides he isn't going to 'leave it'.

My pup was attacked by a pit mix last year while on a hiking trail. The owner had no clue what to do and her shrill screaming of "let go" and "drop it" did nothing. She was next to useless. I ended up having to choke her dog out with my knee before it let go. It was not a good day for anybody.

If you know your dog is reactive and has a strong prey instinct, you need to know how to deal with a worst case scenario (break stick), and ideally prevent it from happening (the muzzle).

As an aside, I was told by the vet afterwards that most pit bulls will release their jaw if you stick your thumb in their ass. Who knew?

https://www.amazon.com/The-K-9-Center-Break-Stick/dp/B004RU81VY

Just a stick to pry open the dog's jaw.

Go on youtube and look at videos of people trying to stop a pitbull attacks. I would recommend you don't because the videos are very upsetting. Stopping a pit from attacking is extremely hard to do, basically impossible. This is why pit bull professionals carry break sticks.

https://www.amazon.com/The-K-9-Center-Break-Stick/dp/B004RU81VY

The whole thing about owning a pit bull is knowing that they are aggressive by nature. You're supposed to be prepared for them to get in a fight. A pit bull owner should always carry a [break stick] (https://www.amazon.com/The-K-9-Center-Break-Stick/dp/B004RU81VY) of some form, to break up a fight and to not get yourself injured. I am not saying this was your fault as a bad dog owner, but what I am saying is it could have been prevented in numerous ways.

These things.

Shove it in their mouth, twist to open.