You bought it from me...lol!
To wire the sub at 1 Ohm, treat the 2 coil wires as a pair of speakers. So, wire the positive wires from the car to both positive wires of the coils. Same for the negative.
You can test the impedance with an Ohm meter (while disconnected from the car) and you should get roughly 1ohm.
Looks like the sub is out of stock everywhere, so while you wait, install the amp and see if you like it with the stock sub. I think you'll be pleased.
Is your wiring suggestion if both the LH amp and SoundQubed sub are installed? Would it be the same if I was to install just the sub with stock UHFS? Or would just replacing the driver not be worthwhile?