Just a point - the Huanyang manual does say NOT to include a contactor between the output terminals and the load, unless you can guarantee no output from the VFD when the contactor is switched. So that adds complexity if you're looking to have independently switched motors.

HP to kW?, just think of 1Hp as 745W (or wet-finger 750W)

Personally, I'd get a cheap VFD for the extraction system.

edit: corrected HP/kW scaling