I would get ahold of these guys. Iirc, Brian is known to peruse some forums, and I believe support diy efforts.
https://www.gikacoustics.com/
Also, not sure if your diagrams are to scale but I would definitely not put the seats in the center of the room. That can be a vacuum for bass, and also you’ll want your surrounds more to the sides than noted in the diagrams. Moving the LP back a little, (but not against the wall) will address both.
Also as DP mentioned, the mirror trick works great. I wonder though, being the room isn’t terribly large if you’ll get good enough results just by having furnishings and the big curtains in there. Seems like toole has done research finding favor in basic room furnishings than full acoustic treatments. Obviously there are testimonies to the contrary but I would recommend going a little at a time and seasoning to taste vs going crazy with a room full of treatments. Nobody likes a room that’s toooo dead.