What happened to my room acoustics

Thank you, @newbee.  I did experiment with varying toe-in angles, ranging from straight to pointing towards my shoulder, to find a trade-off between the width of the soundstage and imaging. I ultimately settled on a slight toe-in that points slightly outside my shoulder without realizing that what I perceived as an 'augmented' soundstage was, in fact, the out-of-phase reflective wave. Surprisingly, I found that I actually prefer a wider and more three-dimensional soundstage, even though it doesn't come with the benefit of deepening the soundstage that I've always wanted. Dr. Toole has asserted that these reflections, including the first lateral reflection, should not necessarily be absorbed.

I did measure the right channel at 3 ft but didn't post it. The response appears flatter, but it has more humps and dips. I'm beginning to doubt the accuracy of the measurement tool I was using...

A suggestion, I start with math for positioning my woofers (Cardas formula) which in your case will be approximately 6.25' from front wall and 3.8' from side walls.

I would then start sitting (on a chair on casters) at a perfect equilateral triangle and roll back (away) from the speakers slowly which will help you find several "semi sweet" spots which you can focus on later on when fine tuning.

Of interest is that you mapped out the "golden triangle" and then didn’t adhere to it.

Thanks @aewarren & @ervikingo. I experimented with that a while ago. If you take a look at my second sketch, you’ll notice the ’golden ratio triangle’ where 0.448W and 0.276W align exactly with your numbers. Unfortunately, I’m not fond of this arrangement. Firstly, it utilizes only 6% (17 square feet) of my entire room space (280 square feet) for the listening area within the equilateral triangle. If I place my Poang chair with an ottoman in that listening position, my feet would almost touch the speaker plane. It feels quite cramped. Secondly, I found the speakers and stands to be extremely intimidating. I didn’t enjoy the setup at all, and I couldn’t sense a spacious soundstage in such a small space. I must admit it’s a setup that I find rather impractical. I apologize for the strong language, but that’s my honest feeling about it.

@lanx0003 No worries, those are suggestions.  They have worked well on my 4 prior rooms and speaker setups.  

The most challenging were the Aerial 8b with the side firing woofers and the Betas since you have further flexibility but I had already placed a huge projection screen which can't be blocked.

BTW, like the Poang but its a bit too upright for my back.

@ervikingo  The almost full-range Aerial 8 is reviewed favorably with impressive specs. It could be an endgame choice. Good luck with them. The Poang chair is a bit too upright for my liking as well. But if I sit further tilted back (on other chairs), I found that the sound perception changes drastically.  I am getting used to it now.