Unless you stand in the middle of the room, you want the mic pretty much where your head is at MLP (main listening position). Use another memory setting on the AVR and re-run MCACC auto, using all channel adjust and the mic where it belongs. Then, during playback, switch between the two memory settings and see if you hear a difference. I'll bet you will.
Understanding the graphs comes one step at a time. Don't try to run through it all at once. Most of us have spent many, many hours over weeks/months/years trying to improve one aspect or another of our systems. Hence, rabbit hole.
Now, the subwoofer is another story.
If you have the flexibility, search for "subwoofer crawl" and do that while you're waiting for your mic to arrive. Since bass sounds are omnidirectional, I doubt it matters whether you have the sub facing down or forward, since, apparently, it's designed for either. It will be easier when you can use REW, but your ears will be able to help you here. And it's good practice.
LFE in from the AVR. Gain so that sub level on AVR is close to 0dB after running MCACC. Then you'll probably want to raise it on the sub (house curve).
If you need help, PM me; I don't want this to get too far OT, especially since it's already been covered elsewhere.