jostenmeat,
I really appreciate you going through my lengthy posts and adding some much needed correction, addition, options and alternatives!
As you pointed out, I put up a whole bunch of posts at once, and I tried to cover a lot of ground. I'm sure you can appreciate that I missed a few things and oversimplified at times.
It was a pretty big info dump, and I wanted to be comprehensive, but I didn't want to completely overwhelm the OP!
So in regards to the room treatments, I tried to keep it somewhat easy and just go with the basics of where to place panels and general sorts of guidelines. Your additional thoughts are great! But one nice thing about acoustic panels is that even if placement isn't optimal, just having them in the room is still a help

It's all about reducing reflected energy so that the ratio of direct sound waves to reflected sound waves is higher.
Part of my placement suggestions went hand in hand with my speaker recommendations though. The Sierra Horizon speakers with the NrT tweeter have very tall vertical dispersion, so the ceiling and floor coverage ideas are a part of that. If speakers with more controlled vertical dispersion are chosen, you're right, the floor and ceiling coverage will be less of a concern.
I'm not sure what would account for our differences of opinion about the Focal speakers. Did you say the ones you heard were an older generation though? That could definitely have made a big difference. Focal has really improved that Aluminum/Magnesium tweeter. I think it might have come from their studio monitor efforts. The CMS studio monitors are very good for the price, and the current Chorus speakers in the Focal consumer line now use the same tweeter. I can't say for 100% sure, but I think if you heard the current Chorus models, they might sound markedly different from generations past. The old Chorus speakers weren't great. So I wouldn't be surprised at all about your opinion if it was the older models that you heard.
The cable/wire Bluejeans recommendation was definitely a case of me simply getting to the end of a 40,000 character post and rushing things a bit

Anyone who's read my other posts around the forum knows how often I recommend monoprice to everyone! I did NOT intend to say it has to be Bluejeans or nothing! But I will say that I do like to support North American made products when the budget allows. And there's something kinda nice about using literally the same cable stock that's used in broadcast studios

But yeah, I completely agree that other brands are just as good from a performance standpoint and make more sense for things like short connections from an AVR to an amp. I think you'll agree that BJC is still great quality stuff though! So I never regret recommending them highly! And they are quality through and through. Great people in that company, too.
As for the whole pixel and screen door effect thing:
completely agree that it's LCD that's the culprit in most cases. I do tend to start to see the pixel structure with 1080p DLP up around 40 degree or larger though, although I actually think it's the other artifacts in DLP reproduction that I notice more. The dithering being the biggest note. But then again, DLP artifacts are largely reduced with a 3-chip design, so I very well might be off base with that one.
The thing is, the JVCs are just so darn good! So I wasn't really even considering alternatives, to be honest. Again, just me rushing a bit because of how much I wrote. But I don't really see a reason to stray from the black level and contrast king

Under $10,000, the JVCs just really can't be beat in those areas. But it DOES take a "bat cave" type of darkness to truly get the best out of them. So a brighter DLP might make more sense. I just think the JVCs are pretty spectacular though. And the new X55R/RS48 brings the JVC blacks and contrast, brighter output than last year (by all early accounts, anyway), AND pseudo-4K to the $5000 price point! So it was really a case of "why not?!" In my book. OP was showing a 12 foot diagonal screen from under 10 feet away in the original drawings. I'd take 4K for that sort of massive viewing angle. That's for sure
The screen material suggestion follows the projector suggestion, but it also has a lot to do with being acoustically transparent. Elite's original AcousticPro1080 material had fairly visible holes in the weave. The new AcousticPro1080P2 is quite a bit tighter. But the AcousticPro-4K looks almost completely smooth. You won't find smaller holes unless you go SmX. And their screens cost almost the entire budget on their own! Or at least about half of it
Perforated screens were already worse than the AcousticPro1080. So it really just came down to my feeling that the AcousticPro-4K material makes the most sense. It's affordable. It's wonderfully seamless and smooth. Again, it's a case of "why not"? It's out there. It's great. It fits the budget. So no real downside
Hope that all makes sense. I would surely hope it's evident that I'm only trying to help

But I appreciate other folks making the necessary corrections and additions to what I can offer. Only human over here. I make mistakes.
Cheers!