We have fostered 17 dogs ajbrown so I can say with certainty that you are doing a fantastic job. Your patience is outstanding and your logical approach to dealing with issues one at a time is obviously working out very well. The truth is there's always a reason a dog has been handed over to a shelter or into foster care and sometimes the reasons aren't pretty, so for instance her aggression with other dogs may be a lifetime problem but if someone can undo it I'm sure it's you!
Not sure if you know this but the person at Paws who looks after nail trimming is a kind hearted groomer who spends a lot of time trying to ensure that the dogs are not afraid and consequently happy to be groomed again. If your dog shows the panic that you describe I'm quite sure that she would stop the process for the benefit of the dog. That obviously doesn't help with the specific problem of long nails but it might be the reason. The solution that we have found to work is to basically trim one nail, followed by lots of love and treats, and then let it go for a day. Over time we found that this worked, eventually allowing us to trim two nails and then three etc.
Exercise... as I'm sure you know a tired dog is a good dog so finding a place where she can run without difficulty is very important and there aren't many places in the villages where that's possible. Doggie Do Run on 301 has a training section that is completely fenced off and quite large (in length) so you might want to go there and talk to the owner explaining your difficulties and training needs and arrange to use that section by yourself. You would be able to throw balls or even try to start agility training there which would occupy her brain and blow off some energy. It's usually one of the quiet spots in the park and is definitely the area where only one dog is allowed in at a time.
I was delighted to hear that you have trained the dog to be comfortable in a muzzle. It shows great responsibility on your part and undoubtedly protects both of you in the case of fear aggression but did you know that there are soft muscles that have the benefit of not making the dog look ferocious? Sometimes the very look of the cage sets other owners into a fearful mode that can be reflected in the behaviour of their own dogs and a cycle of nastiness can start to happen. The soft muzzles are very effective and sometimes go unseen by other people... just a thought. Aggressiveness may just be part of her baggage though so finding a place where she can run and you can both be happy is pretty important . I know people who go at odd hours to the area behind the polo field specifically for this reason. Maybe that would be helpful for you as well .
One last hint... we have found that new Foster's being trained almost needed a training "outfit" so we have a harness that we put on them when we "mean business". It's not for punishment and it isn't harsh (made of soft material) but it just gets their attention, sort of like a Service Dog putting on their work coat. We have found that the dogs seem to know the difference and stop pulling or feeling panicky... maybe it makes them feel more secure because someone is in charge but for whatever reason, it turns a pulling lunatic into an easy dog to walk and an aggressive dog into one that can pass other dogs without the need to show their dominance. My theory is that it works a bit like a thunder shirt but that's just an opinion. Whatever works!
I can't tell you enough how wonderful you are to put all this time and thought into Z.... I'm sure you will enjoy her for years!
