1 Year old female is always on guard.

So we have a 15 month old Pit Bull female, a 5 year old neutered Plott Hound, and a 7 year old Male Beagle.

We used to have a 12 year old female Labrador, who sustained a slipped disc injury around 2 months after getting the Pit puppy. Nursing her got in they way of a lot of important early training. We had to put down our sweet Lab after 3-4 months of physical therapy because her body was deteriorating and rehabilitation wasn't working, it was a hard few months, and towards the end, a stray Beagle came in with mange and needed nursing too.

Even after all of that, Goose(the Pit Bull), has always been eager to learn. She is quite stubborn all around, and quick to revert back a few steps in training. For example, she never showed signs of food aggression until a month or so ago, she knows "leave it" and does not start eating until the person feeding her gives her permission to. Even with that, she pierced the Beagle's ear over a piece of food that fell out of a dog bowl, and she broke our cat's tooth over cat food! We have her food aggression under control, but not all bullying, she is still quite greedy over toys. If our Plott Hound has a toy, that's the toy she wants, he is smart and knows to go for the one he doesn't want to play with first, but she still will sometimes go for those toys. They all understand that the toys belong to us, but once we start playtime, that's when we start to have issues. She also has recently started pulling on the leash, which she didn't have an issue with until around the time the food aggression started.

Which brings me back to the title: if she hears a noise outside, if she is on the porch, or if she is in the field on a lead; she is on guard. This was really the progenitor of bad behavior. She saw a stray cat in yard one time and now is always looking for something. We give her plenty of stimulus and spend around an hour a day with training, but we are at a loss when it comes to this. Her leash training is improving daily, and her understanding of commands and boundaries is constantly improving. I have been around dogs my whole life, and have never had one this difficult. I've always lived in the kind of area where people drop off unwanted, neglected, and abused pets. When i was a teenager, we even had a dog show up that had been used as a "bait dog" who was scarred from a life of maiming, even he wasn't as difficult as this little girl has been.

Any advice is appreciated, and I understand that this is because of my shortcomings as a dog owner, we just really need some advice!