Last year I moved into a new home.
It amazes me how many of us here have moved to a new home in the past year or two. AND have questions similar to yours.

Manny, when I first took over my little space in my new home, I was terrified, but happy to finally have my own space.
I have two window walls to deal with. It was the only "my own" space I could monopolize. I have ceramic tile set on concrete with drywall everywhere else.
It has worked out fine.
Thick rugs for me, some sound absorption, a bass trap and I am still considering how to work the ceiling. My ceilings are nine feet on one side and almost ten on the other, drywall/plaster - reflective.

You might take Dennis' response and just start adding some movable (DIY? Maybe?) acoustic panels. Move them if you see fit, using what you can hear as a guide at first.

There are many here with far more knowledge and experience in setting up a listening room than I have. I feel certain that many will chime in and offer something useful.

Is there any way you can use "Paint" or some kind of drawing software to create a basic outline with walls, windows, doors, stairs, furniture etc?

Your mearsuring already gives me the feeling that there is much you can do to help balance your room for better acoustical response.

I was terrified that this would NEVER work when I first moved in, but I have had some great listening times with my iffy room, after some work.

I wish you good luck and congratz on the new home!

It has been 16 years since my last move, but I remember having to deal with room acoustics from the beginning. Anything that you can think of is usually worth a try. interestingly enough, even tilting the speakers back a bit was useful, or finding a way to put something like a pillow in front of them on the floor, just to hear the difference. Pillows are useful this way as a temporary way to find where treatment might do the most good.

Hey Manny.

Dimensions? How long is the stair wall? Length from stair wall to opposite wall?

Wow, lots to work around. The corner system setup makes some sense to me too all things considered... I would add unconventional toe angles and speaker spacing to 4Ks idea of playing with the speaker angles... maybe make reflections more complex and diffused. I wonder what else you have tried for system locations. The drop ceiling really messes with me. I wonder about using it more symmetrically and treating around it some, like 45s in the "corners" between 6.5 and 7.5 foot areas. In two of these ideas below, I was imagining using the stairs like Steve does... an opening centered and behind the speakers. But that 6.5 ceiling part, no room expert here, so out of my range for conceptualizing effects and work arounds without playing with it sort of methodically.

Thanks for the input, everyone. I haven’t tried Will’s first two suggestions as they require taking the bar out but did try the third, as well as centered on the long wall and centered on the skinny short wall (180 degrees from Will’s third suggestion). So far the corner is best sans removing bar.
I purchased some carbon and foam today to start the diy absorption process and some heavy 3-layer drapes to cover the windows with.
I’ve played with speaker placement a fair bit but have admittedly lost patience. With all the busyness of moving when I get a chance to listen I only give two or three adjustments before taking the time to enjoy the music. I feel silly realizing now that I haven’t adjusted the baffle angle at all. My baffles normally sit at about 14* and I know the sound changes dramatically as the angle reduces. I’ll add that to my next adjustments.