Now I can appreciate your frustration, and I feel bad for your situation.
Not sure waht kind of filtration you have in your 60 gallon pond, but it doesn't sound like that is the problem. To start with, your pond could be a bit small to start creating a balanced ecosystem. It does sound big enough to at least start a well potted water lilly in a container for water lillies, and place it on the bottom.
My fairly new 365 gallon pond has been in since last fall and right now I have one older water lilly that is several years old and two new ones that I just put in the pond this last week. The older lilly is sending it's first three lilly pads to the surface. I have found that the plants help create a healthy balance in the pond, and so far I have never had to medicate any of my indoor or outdoor fish.
Not sure what you should do with your existing pond fish, but I would at least get some healthy plant life started in your pond before you add more than one fish in your pond until youe plants are established. That shouldn't take to long. The fish need the natural plants and the plants need the fish. It's all about finding in balance in your pond.
I have a had heavily plants aquariums in my home for almost thirty years now, and I have enjoyed the beauty of an aquarium green with healthy live plants and compatable fish. As a newbie to outdoor ponds, I'm sure I might be on to something with the plants.
I hope this was helpful, and that it works for you.