I have a 2004 Envoy with the code P0526. My water pump is good, I'm having to put water in the radiator every other day, but does this all mean that the fan speed sensor circuit is really bad or could it possibly be a simpler fix?
You have a leak somewhere. You should find and fix it.
The P0526 means the fan clutch is likely bad or something in the wiring for it. It would not be related to your coolant loss. It's common for the wires from the connector to the clutch to rub and chafe as per this image.