I am using a continuous servo to drive the pump, which is a piston pump, it has to overcome boiler pressure. I am waiting for an auto boiler control to arrive, but I was going to test the servo driven pump off the radio while I am waiting for delivery....

This is a relay switch that can turn on it off smoke, music, pumps, lights basically two relays that plug in a Servo port. Clean n cheap on eBay.

Is the pump a water pump? if so I use a esc for my water pump that way you can just plug it into any cannel. hope this helps.

the confusion and frustration you are experiencing is one of the main reason I switched to Flysky, I now use a FS-i6x and a FS-ST8. I am putting my new Spektrum TX16S up for sale.

In settings each switch position has a setting right now you have switch on n off doing sane thing. Go to the switch and see on screen it says 100 or a number then switch the physical switch It will have same number but dial it a bunch so Servo arm moves. The physical switch when flipped will move as you set. In flaps it goes 100% + or 100% - spectrum manual is on line fyi if u don’t have it. Look up setting up flaps. Also the wing has to be set fir flaps and the switch you use assigned fir it. Manual will show you. It’s easy. I bought this item it plugs in as a Servo but has two relays the from centered will flip. Easier to use