I'd really like to know how to interpret the RT60 chart myself. Mine doesn't look anything like yours does. Mine just looks like random, unconnected slashes, tho I haven't looked at mine in a long time and there have been updates to REW since then.
I get a rough idea of what your fr looks like based on the waterfall chart, but you didn't actually post it...
If you get a pair of pros you can make some adjustments to shoot for a flatter response. Then again, maybe you can now. What other gear are you running? A more detailed description of your room, seating distance and gear would be helpful. Post up your spl only fr chart too!
*Edit: Your low bass response based on what I can see does look pretty smooth from 70 hz and down with what looks like a built room curve. What all have you done for eq in those charts? Any? Room corrected, pure direct?