This is hard to parse.... because your supplied measurements are with EQ in use, correct? (you said it's all controlled by a mini DSP) It is not possible to make good comments on the room acoustics when EQ is in use.
So, because of that, I can't help at this time, but... I will put a few things out there.
The room is a swell place to be, feels nice... unfortunately the stuff that makes it nice is playing huge havoc with your sound, if my past experiences are indicative...
2 walls, half the room, is lined with floor to ceiling resonance generators, also called 'bookshelves'. Fireplaces, cabinets, closets... ANY 5 sided structure in the sound field will make a resonance. And you have a lot of them all tuned to the same frequencies. I wager that is your likely primary offender at this point. But as I said, if your measurements are while using EQ then you are hiding/altering the issue, so I can't really see the truth.
Looking at L & R you can see dips and bumps in the base response that are not there in the nearfield, this is room modes and resonances in action. It is impressive how well they even each other out by the listening position in stereo. Leaving the 17db rollercoaster bit in the middle. This section also looks created by room mode/resonance, I would lean heavily towards the resonances/bad reflections side of that in my search, and that would aim my focus at the TV, the bookshelves, the speakers over there on the right, and the whole lump of gear is a bad acoustics bit being right there.
If I were you I would not rush to go buy more acoustics stuff, I suggest spending time and attention on figuring out how these room elements are effecting the sound.
Do you have any of those old school flannel lined square ended sleeping bags? Those things are like a black hole for sound... put one up on each side... covering the gear and TV and covering as much bookshelving as you can and see what happens to the measurements. You should also chuck a thick cotton or wool blanket, folded up, on the leather foot stool unit.
While I was doing my small room I came across all of these issues (and many many more)... I had bookshelves, 2 of them, 2'x6', in the back of the room. I could not get one bass note to behave. Eventually I decided to redo the back of the room ( I had done everything else pretty extensively), now here I'll state that the key play when doing acoustic treatment is to have music playing when you install parts, as you can hear the effect it has in real time as you put the item in place and take it out. As I removed books and moved the shelving I could hear the bass note cure itself...This lets you know it's going to do something and where to listen (frequency), then sit down in 'the' spot and listen to the effect of the new stuff. New stuff is not always a win, like, if it has no effect in said spot, don't put it up there, and if it has a bad effect, like it dulls the tone in some region, it's not the right solution. For me doing this is something of a piece by piece process so you can be positive about each step you take. If you just go and put up a whole room full of stuff in silence and then listen and it's junk... you won't know why...
I have a friend who is smarter, more wealthy than me and has been a dedicated audiophile for 40 years. Went to hear his 50k system. I noticed a bad resonance in the sound. I didn't say anything... but he offered there was a bass problem and he needed to spend 40k on Pass amps to solve it. I said he didn't have an amp problem and the bass issue was not the Magico drivers being diverted by rebounding sound waves, as he theorized, but I wager the issue is the two driverless 12" 3 way speaker cabs from the 70s that he had holding up the TV against the wall between the speakers (4-5 feet out from wall). He looked at me like I was fking insane. I badgered him once to get them out of there, it's cheaper than two Nelson Pass mono blocks, will take less time to test than it takes to order two mono blocks... Eventually he did remove them and the bas resonance was gone. Now he needs the amps because of no micro detail.... which is also an acoustics problem, not an amp issue...
Back to the beginning, if you are using EQ as you go while trying to sort this... IMHO you are making it way harder to solve. Best to do acoustics work without any EQ. But I also hold that EQ should not be needed for a stereo and is a negative in every event.
It is doable to passively treat a room and get flat response without EQ.... for everything above 200hz give or take, and to my ears when that is done right it beats EQed sound 1000 to 1, to my ears DSP EQ sucks the life (musicality) right out.
The only thing that requires more is bass... and while 99.999999999999% of people will banter on about bass traps... I am not one of them, because passive bass traps do not trap bass, actually, nothing does. If you had giant room mode problems I would talk about my active bass solution that has nothing to do with DSP or altering the signal to the mains in any way shape or form. But I guess I'll wait until you post the same but with a subwoofer involved, as I reckon if room modes are gonna show up, they will then...
Last note... absorption and resonance treatment for sounds that are a negative contribution (first reflections, weird features in the room etc) and then diffusion to create the sound stage/sound scape. both must be used with ninja like precision.
Acoustic solutions are not voodoo, just wildly complex physics... but once you get a grip on it all it can be sorted with a reasonable amount of money and simplicity, especially via the DIY route, which in most cases is the wise route because few of us have pure clean walled rooms to work with, so custom shapes and sizes for absorption units and diffusers is often the ticket.
And lastly, if you had more omni directional speakers your room would be soooooooo much worse, but being all horns you are pretty well minimizing sidewall and stage wall interactions. But he back wall should be able to absorb a lot of sound to keep it from returning into the listening area.
Perhaps one or two of these many words will help, if not, apologies for wasting your time.