F12 and Sierra2 measurements ?s

[SAFETYpin]

So I'm trying to wrap my brain around as much as I can. I see these same types of posts all over and I've tried to glean what I can from other newbie questions but I can't find "enlightenment".

So, I'm having difficulties understanding all the settings on my F12. Particularly when compared to some of my measurements.

Subwoofer Larger Graph
Round 3 sub settings.jpg
Is 1/3 octave smoothing appropriate while trying to interpret these graphs or is it masking too much detail?

Sub Settings
PEQ=Off
CrossOver is as described in the legend (X50hz or XMax)
Delay/Phase=12oclock (Set without reason)
RumbleFilter=Off
ExtenstionFilter= HI/14hz

AMP Yamaha A-S801
Sub out has a fixed 100hzLPF and no bass management for mains R+L...

Should I turn on the rumble filter to try and tame the bump @ ~17hz?
Which of the Sub measurements looks best for 2.1ch music?
Anything else that stands out as obviously in need of attention?

What does the sub-woofer line in low pass filter do, and how does it relate to the crossover dial? I've measured the difference between all the settings but I don't really understand why or how.

Mains+Sub Larger Graph
Round 3 spl graph.jpg

Should I just be focusing on trying to make the response flat?
Is my sub gain too high? It appears pretty high in the measurements but I don't hear much output from it unless I'm specifically playing bass heavy music.

I assume the rise @ 55hz is room related.

Anyone else have measurements of a well sorted setup to share?