Correct. But you could just use 1 for mono out.
I can't access the web page but yes that should work. Load box connected the speaker out, and hopefully the HB has a line out connection which you would run to the return or input of the HX.
I would use the 2 outputs on the HX FX to FOH. I believe you can put a Cab IR block at the end of your signal chain. Use 1/4" to XLR cables to run a mic cable to mixer.
I'm not running to FOH (don't play live anymore) but my set up is similar other than I don't need a load and can use the Mod 50's slave out. I'm using a W/D/W rig but the set up is similar enough.
Gtr -> HX FX Input -> FX loop block send to Mod 50 input return from Mod 50 slave out -> stereo effects on HX FX -> HX FX output to stereo power amp.
Trying to figure a way to run my H9 in the loops of the HX Effects (in stereo) but also run 4CM with my Mod 50 in a WDW rig. Outputs would go to the wet power amp. Can I do this with a GRX4? or other loop switcher?