Sorry for the noob question but if you are sending audio from your interface output on 5/6 stereo and going to your h9000 on 1/2 why does the ableton device say audio from 5/6? (I was expecting to see 1/2 here) Unless this mean you’re also going back into 5/6 on the input side of your interface?
Ableton output refer to the specific outputs on your soundcard. For example on my RME UFX the ADAT outputs start at output 13. The ADAT cable goes into my H9000 and they are channels ADAT 1-8 on the H9000.
Ableton has no idea what external devices enumerate devices as. It only knows what soundcard output to route audio to. Your H9000 has no idea what ableton has labelled the outputs, it only knows it’s own input channel layout.