I am no expert but that dip at 80 is likely room size VS seating position and not easy to get rid of, the good thing is in real world listening it is not a huge deal if unable to eliminate it.
Did you sweep the mains up to 20K.
Once you play around with REW and room correction for a while, my results were that room correction does a excellent job with distance and a good job with level matching......other than that, not soo great.
Does your AVR have EQ for each speaker ? How many bands ?
Does it have EQ for sub, how many bands ?
I found better results setting the EQ for the mains myself and it produced a sound I liked better.
I found best sub results with a Minidsp as most AVR sub EQ`s are pretty limited.
While not rock concert levels, the sub seems to get some room gain and lower extension for what it is.
Next time you get to play around..........set all crossovers to 80hz, disable room correction and do some full sweeps up to 20k, then turn room correction back on and compare.
The best room correction for a sub is location and then DSP/EQ.......
Now that you have REW getting mains dialed in for better sound is also possible...or at least see what they are doing and determine exavctly your preferred sound signature with your speakers in your room.....