Yes, our S-Bus inverter can be powered even with 15V supply so 2S is without any problem.
Channel numbering does not need to match as each manufacturer has different numbering.
You can connect Throttle (ESC) even directly to the receiver if you are not using governor from the unit. In case that you are using Governor, you have to assign Throttle. Mostly it is Channel 1 in the software.
If you have external BEC and AUX and RUD ports are already used, you will need Y-cable.
With PWM (classic) connection Y cables are not needed as the power is always passed through the receiver where you have mostly lot of unused ports.
This cable can perform very well:
http://www.conrad.de/ce/de/product/2083 ... 3?ref=listIf you will need more free ports, you can use our new Spirit Pro, it is great for bigger helicopters.
You are welcome!