I don't want the pump to be damaged by the freezing ice. Some pumps have gaskets that shouldn't dry out and I don't know if mine is one, but just to be safe-----. I don't know anything about UV as I don't have one. As to when I take out the pump, it's when I see the ice start forming on the waterfall. So it could be anywhere from October to December. I just don't want an ice dam to form and end up pumping water out. I do have a float on my pump so even if it did get pumped down a bit, it shuts the pump off so there's no real danger.
It was 70 here yesterday so I too am still feeding the fish. Mine seem to stop being interested in the food eventually so they kind of give me a signal. But it won't be long and 50 is a good temp to use. Some will say lower temp. You do realize that none of what I'm saying is set in cement, don't you. We all differ in how we do our ponds but we all agree that our end goal is the health of the fish. If it works for you, then good.