No worries about hijacking. I was wondering that myself.
Here's my first theoretical EQ effort, taking some of Wayne's advice and lowering the target level to 73dB to try and deal with the low-40s null, which I assume is a room mode. I moved the sub around a bit, including into both corners, and didn't see any change in that area. I didn't bother filtering much above 100Hz, as I'll likely be crossing over well below that.
With a bit more time for tweaking, I reckon much the same response could be had with a couple less filters. But I gotta go earn a crust. Stupid real life.