That graph makes PERFECT sense! You have a big drop starting at 150Hz and going quite down in the sub lows.. which is why you have compensated for this in your mix.
Homework:
Do the following in this order:
- flip phase on sub, measure room.. probably not going to do the trick but worth a try
- put sub on stable chair in mix position.. play a track of basslines and crawl around the room till the bass seems the most constant and strong.. put your sub there.
- measure room response with phase in and out of sub
- try moving satellite speakers away from the wall
- move, measure, repeat.. it took Bob Hodas 8 hours to find proper space for sub and speakers in my A room!
Also, what are the dimensions in your room in ft?