If I remember right you found the pup, and quite skinny.
The food aggression is definitely to be expected---but certainly not to be allowed. Mud was a rescue, and had been extremely malnourished. When I got her, she would snarl in an almost terrified manner if people were very close to her food(with her in her kennel for the safety of everyone), and dogs couldn't get within 6-8 feet of her kennel without her lunging at the bars in a snarling frenzy. The more she learned the trust me, the better she was with people...but I still worked just in case. I would pass by randomly and drop a really tasty treat into her kennel. Pretty soon she went from thinking, "This person could steal my food!" to "Hey, everytime a person passes, the ceiling spits GREAT treats!!!" From here I opened the kennel and would toss a treat into the kennel--my hand was much closer to the entrance here, so boundaries were much less defined. This went on until I trusted her enough to stick my whole hand in her bowl, move her food around, move the bowl around, etc. It only took a day or so, as she wasn't too worried about people after she trusted them.
As for the dogs...again, for her safety and since I didn't have a helper, I kept her in the kennel. Since she lost it with a dog 6-8 feet away, I leashed one of my others and paced 10 feet away. I'd play with this dog and walk back and forth, watching out of the corner of my eye to check her body language. She wasn't concerned, and if she was completely relaxed then my canine helper and I casually eased in a bit closer(a few inches,
maybe half a foot). If she wasn't quite happy but still calm, then we continued to ignore her, playing and walking at this distance only. When she relaxed and was staying relaxed, we came in a little closer, still not paying attention to her and just off in our own little world. Again I waited for her to stay relaxed, and we continued this process until we could circle her kennel with her completely happy.
When she was consistently calm with other dogs all around her kennel, I took her out, and leashed her. I was confident that I could handle two dogs(if you're not sure she won't have an outburst, then have another helper with her on a short but loose leash so no accidents happen), so I leashed her, left her in the kennel, and lead the other dog past the open door(not entering, just passing). I continued this, making sure that she was completely calm and relaxed, and then lead her out. I led the other dog to the entrance, then back to me, to the entrance, then back to me, then in...if she was still calm, then I lead the other dog out and then back in her kennel. She was doing marvelous at this point so I shut the other dog in her kennel with her sitting outside of it. After this I took her food bowl out and let the other dog poke around it, sniff it, stick their nose in it...etc. This way there was only the bowl to worry about, rather than bowl and kennel. (She had become rather kennel aggressive because her fosters had fed her only in the kennel for obvious reasons...but it had caused her to worry about dogs near her kennel with or without food.) Any signs of aggression were corrected with a gentle but stern, "Ah-ah!"
Once she's doing well, you can repeat the random treat dropping trick, but this time with your canine helper. Soon she will associate people and dogs with positive things, rather than fearing her food will be taken.
You can use this same method with the toys. Her behavior could be for a variety of reasons. In former neglect cases, it is usually fear aggression. They've never had regular meals before and they worry that this could end, and feel threatened by other dogs and many times also people. Sadly, COUNTLESS dogs are put down in shelters because of severe food aggression. If she will allow you to handle her food, IMMEDIATELY remove it if she shows aggression. Give her time to calm down and then give her a good relaxing massage or just wait until she's relaxed and happy. Then and only then does she get her meal back. Never feed her in an unstable state. Make sure she is relaxed and calm before feeding.
If it is not a fear-aggressive type response to her food and toys, it could be a dominance issue. In the wild, the alpha ALWAYS eats first. When the others come near, they're insulting her alpha position(if she's dominant in nature). From the sounds of it, to me it sounds more like a fear aggression response.
You mentioned that the hackle raising didn't seem like a big deal. DO NOT let her get by with ANY signs of aggression. It's very important to stop the behavior at the very first sign, or before. Pay very close attention to her body language. The sharp, "Ah-ah!" could either stop the behavior or set her off in that situation. Since I can't see for myself that's hard to say.
But, it's okay for her to have her own toys. My dogs have designated toys for other reasons, though. Zeke's a snuggler and loves stuffed animals and tennis balls. He's not a tough chewer and toys usually last him forever. Rusty's an incredibly rough chewer however, as is Mudflap. Their toys are expensive and it's really hard to find ones they can't destroy in a few days or a week. Nick's a teacup chihuahua, so his toys are very small and he's like Zeke--not a tough chewer. Not only would they destroy his toys, but the squeakers and size of the toys would be dangerous for the 3 bigger dogs. Therefore, my dogs have designated toys. They know to only chew their toys and leave the others alone. I taught this by "leave it" and also by simply a firm "Ah-ah!" when they went for the wrong toy and rewarding them with their own when they left the wrong one alone. They aren't possessive at all, and they are happy to play with their own toys. It's worked out quite well and no one bothers anyone.
If you choose to use the "Ah-ah!" remember that it is not supposed to be yelled or snapped at the dog. It's just a quick sound that usually gets the dog's attention. I use it at a low-normal volume and it's all I need to discontinue any unwanted behavior if the dog is doing something a distance away. Let's say Mud was about to pounce on a yummy hydrocodeine pill and I was just coming out of the next room a good distance away...with a simple, "Ahh, leave it." she would immediately stop and leave it alone so that I could come get it.