Where it falls apart for me is that the ATO plug is 4 wires, the float switch is two. I wasn't sure if the other two wires were related to the relay circuit.
So in this case you are setting up the relay as a separate power bar/outlet, that makes sense to me, although it confuses me even more about why the ATO would need 4 wires...
I'm into some homemade 4-year old corn whiskey myself, which probably isn't helping...
The float switch can be wired into the gnd and IOxx Pins on the jst plug for the ATO. The other two wires aren’t needed