Need help with room and speaker setup, big dip from 250-80hz

This may not true any more depending on the vintage of your RS meter, but they used to be known to need a well documented adjustment to results to adjust for variations in its ability to measure at differing frequencies. Search online and you'll find a table that tells you to add or subtract from each result (e.g. "at 80hz +3db"). I think the adjustment is based on limitations of the built in microphone. 
Squarish rooms are tough, although with a 3' tall half wall, higher frequencies might act as if you are in the "bigger room" ignoring the half wall. Many speakers manufs. suggest a diagonal setup in squarish rooms. Could be worth a try if everything else mentioned doesn't work out to your satisfaction. Cheers,
Spencer

The port on these speakers appears very small, and could be causing a reflection off of the wall/corner that effectively cancels out the frequencies you mention.

First - remove the bass traps - temporarily

Try different distances from the wall with the speaker toe-in at around 5 degrees. Keep the speakers about 7 feet apart to start with.
 
Once you have reasonably good bass performance try varying the space between the speakers and then adjust toe-in for a final adjustment

Once you get a pleasing sound re-install the bass traps to see if they are over compensating on certain frequencies

You may then need some minor adjustments for best sound once the traps are installed
 
I have a pair of studio monitors that suffers from a similar problem - they required over 1 meter of space behind the rear of the speaker, but since I did not have that much room, I ended up installing a cowling over the port which redirected the airflow downwards. This seemed to resolve most of the issue - the rest was remedied with correct speaker placement/toe-in.

I can now place the speaker much closer to the wall - i.e. down to 8 inches

My speakers originally came with a foam plug for the port that helped a little - it did not stop the airflow, just slowed it down a little

Personally - I do not use meters for two channel systems - I let my ears be the judge.

I do find a meter helps greatly with Surround Sound systems

Regards...

First of all, thank you all for the input. I spent a few hours moving my speakers around my music room, trying to move the speakers closer to the front wall, closer together, adjusting the toe, etc. I was able to get varying degrees of success but I still had massive nulls throughout the frequency range 80-250hz. I finally tried moving the speakers further out into the room. My reasoning was that I had good bass response below 80hz so I could lose a bit but hopefully still be within 3db of flat. I also moved my speakers further apart so that I was listening in an equilateral configuration. The results were better than expected. From 20-1000hz, I was within 3db of 70db. My only small null was at 800hz where the response was -6db down.

Sir

You have not taken the floor or the ceiling position out of the equation when you moved the speakers. You moved the speakers relative to the walls not to what is above or below. All speakers have a speaker floor bounce cancellation relative to the distance of the bass driver. You can have much the same cancellation from that same driver to the ceiling though at a different distance and frequency. If your monitors can be placed on the floor or on  shorter or taller stands or supports for testing this will give you more insight into a placement to reinforce the frequencys you are in search of. Tom

tboooe - have you tried putting the speakers against the 3ft wall?

If yes - did you still get dips in freq response?

What is on the floor? if it's hardwood - try a rug in front of the listening position.

Regards...