I bought some Owens Corning 703. Now what?

In looking at your room diagram, I was wondering if you notice any sort of channel dominance or time alignment/phase issues being made from the right wall: I think the bathroom is along that wall.  I ask because of how close and oddly comprised that wall, and area are verses the left side (from couch position).  I would think you would be hearing or experiencing some different characteristics from the right verses left channel.  I have a slightly similar issue in my listening space, only drastically more profound.
One test I did to measure and see how dramatic the difference was, I played a simple instrument tone from violin or any stringed instrument.  I disconnected one channel/speaker and documented sound qualities, characteristics, feeling, essence, issues. Then swapped and did same with other speaker only, and did same process.  It was amazing how different the sound was coming from each speaker because of the asymmetrical distance to walls.  Granted to be noted this would change again when both were playing (phase, cancellation, other time delays, smearing, etc)  but this gave me a very accurate and dramatic test to at least find ways to contend with my one odd wall due to distance from speaker to it, verses the other and it's vastly more open air. 

I would wonder if going dramatic with this test, and then use all the panels along that bathroom wall to just hear if and what difference there was to just know/have as reference.
I think your and other members thoughts on the ceiling are spot on!
Behind the speakers I want to remember would help with focus and again, smearing/blending. 

Best of luck.  Any room acoustic improvements produce vastly greater impact on your listening experiences than anything.

Sorry I did not read all the above suggestions so the may be a duplication. I too bought a dozen pack of the exact same material,
assembled a frame and wrapped with a soft fabric color keyed to the wall colors. The immediate improvement was dramatic.
Positions to try: Ceiling reflection spots between speaker & seating.
As you have no side reflections that eliminates the 1st ones otherwise needed. If there is a wall behind you add a couple there.
Same for the area between the speakers. Glass surfaces are bad and benefit from attention as well. How many you need will in total will depend on the amount of existing absorption material in the room. You have carpet so that is very good. 
Smart question. Good luck!

@amtprod It’s a good question, but what is not evident from the diagram is that the right speaker, nearest the bathroom wall, actually fires into the entrance way which forms part of the front wall. In other words, there is no first reflection point (as revealed by the mirror test) on that wall.

I went and measured differences in the room. In actuality, my right speaker is 12’6" from the right wall and my left speaker is 15’ 3" from the left wall. I’m not sure that the difference there (3’3") is enough to cause a big difference. Both are far enough way to not be able to smear the direct speaker sound reaching my ear from about 8 feet away.

I will try your test. Yesterday, I did put my panels along that bathroom wall just to see what changed, and there was no apparent difference. Again, because there is no first reflection point there, so that is probably the reason.

@chorus Thanks for your suggestion. Ceiling seems crucial!

@hilde45  Oh I see.  Yeah from these measurements maybe there isn't much if any reverb/cancelling/smearing from the asymmetrical room layout (to some extent).  Try the test anyway, just to see and maybe it will help identify other sonic issues as well.