The noise caps are for audible noise, vibration or hum of the pipes, not EMI. There is no EMI noise generation by induction motors, and they are virtually immune to EMI. The water pipe carries the sound quite nicely when there is a problem. I've had that experience plenty of times.
Franklin does list transformer sizes for single phase elsewhere, and about 3KW for a conventional transformer is what they recommended for their 1/2 HP pump and motor.
The caps page is for replacement start capacitors, not run.
Adding capacitance on the power BEFORE the time delay start relay in the control box, as buickanddeer suggested, is not going to affect the contacts or make them fail. Still, with no good personal experience on capacitance values and how much they will improve start surge, I guess Stevo42 should just skip that for now. If the genny struggles badly to start it, I'd start by adding 15 or 20 mfd of run cap and see if it helps.