Double bass is bad if you don't know what you're doing. I would set all speakers to SMALL with a crossover at 80 Hz. Start there and rerun Audyssey before making further measurements. I think REW works best if you set all speakers to SMALL and let the receiver handles the bass management. If not satisfied, do a sweep of front speakers alone with no sub. Then disconnect front speakers and rerun REW for the sub alone. Find a suitable cross-over point, rerun Audyssey calibration. Connect sub and speakers and rerun REW.
I would turn off dynamic volume, that does odd stuff and I do not use it nor would I measure it. I think it cuts the peaks to keep the volume at a more steady level. I think it purpose it to keep commercials from being loud.
Dynamic EQ does some interesting things. With my Dual ULS-15's it cuts the output below 15hz which I like. I believe below 15hz is a waste of power unless you are putting out massive SPL.
Try Audyssey off, Audyssey on, Audyssey on with Dynamic EQ. They were the most interesting graphs. Overall I found Audyssey to help the graph and sound.
Good luck, love to see more graphs. You may want to separate those subs to smooth you FR. I know that may be difficult.
-34 is low yes but it could mean that the adjustments on the AVR are set slightly high also. For getting a response measurement that should not be an issue if your meter is calibrated to 75dB or other target your using and it is not clipping the input.
The hole caused in the 120 range is odd. I see that a lot I wonder what causes it? The Audyssey I believe does a good job. On my system I leave dynamic EQ off. It raises the 20-30 hz range up high. On some movies it is OK on some it sounds boomy, normally what is annoying is deep bass on music in the movie. I go with Straight Audyssey. On yours it also raises that range how does it sound to you?
I think I would mess with your crossover. I might push the Sub limit higher, I have the limit (I am not sure what it is called) at 120hz. In might fill that gap.
like how the sub if flat out past 80. Mine follows the target line down which in theory is good I am not sure how good it is in practice. I am considering an MBM to fill in that area.
What sounds best to you? I believe I am familiar with your setup, Bonsai tree?
Can you separate the subs? I would be interested to see the results even if it was just for a test and they could not be kept there. I realize that is a tall (or heavy) order.