From my limited observations, it sounds like her respiratory system was first to be comprised in some fashion, which is now resulting in exercise intolerance (paralysis), and along with other associated problems such as not being able to eat. The green feces you're seeing is a probable indicator of excessive bile production which increases in an anorexic state. There are too many possibilities, to narrow down just one without diagnostic tests, but aspiration pneumonia, foreign blockage, collapsed lungs, aspergillus, are some of the possibilities the need to be considered.
In consideration that she was allowed access into your goldfish pond, that would raise the concerns of bacterial diseases such as Pasturella, or Botulism, both of which can result in the symptoms you describe.
The immediate goal with a dyspneic duck should be establishing higher oxygen concentrations, by setting them in an oxygen cage; since that's not achievable in most households, it emphasizes the importance of getting her to a vet - if you have other vets in your area, that you haven't called, you should try calling them as well.
I wish there was more that we could do in such as scenario, but unfortunately, there is not - I would move the bird into a dimly lit area and try to achieve a slightly higher temperature by setting a heater, or heating pad near, but taking caution not to overheat her. Mucosal membranes dry out quickly when a bird is breathing at such as rate, so a higher humidity of around 75% is suggested. Adding some electrolytes to her water, or poultry vitamins would be good to help maintain nutritional and hydration status until a vet can be seen.
