the fuel pump will earth to the chassis. It absolutely will not run down the length of the car as a wire, and it absolutely will not be connected to the ISCV

There is no possible way a fuel pump can burn out an ecu, because it is not connected to the ecu. ( and only a very very very silly person would try and connect it directly to the ecu )

The ecu will trigger a relay, and this will provide 12v power to the pump when required, which will be wired down the length of the car.