This is pretty much exactly my experience as well! Both me and my partner have a lot of gut issues and have very restricted diets. She has several auto-immune diseases and I personally have confirmed mold toxicity, which makes me over-sensitive to almost everything.Gately, I am sorry to hear about your woes. They sound familiar -- my partner has had Crohns for decades. She has to be extremely careful about supplements to scrutinize every inert ingredient as well as the capsule in order to avoid major problems. SHe found that completely separating her meals into "meat" and "carbohydrate" with no overlap of the two, and taking the meat meal first helps her cope. She practices OMAD at least three days per week, not having her first meal of the day until around 6pm. She is an expert muscle-tester and that guides her food intake -- some days she can have a particular food and other days her body tells her definitely not.
Other than to make a comment about OJ, the rest of my response will not deal with nutrition. It is very important to not have reconstituted juices of any kind, especially 'from concentrate'. Research 'flavor packs' and you will see how the nutritive value has been removed. Reconstituted juices are made with water that is often fluoridated, another toxic stressor for your guts. Based on our experiences here, I would not recommend nearly any foodstuffs that could not reasonably be considered of 'Organic' grade, and definitely nothing labelled Organic from China. Curiously, 'pork' products of more dubious quality have been tolerated OK; they just do not taste as good ;-)
I will bring your attention to electromagnetic fields (EMF) and mold exposure as two things that we have unfortunately had a lot of experience with, exacerbating the Crohns (flareup with major fistulae). By EMF I mean not only wifi/cell but also cordless phones, bluetooth as well as the electrical wiring in the house. Such "low" levels of EMF are biological stressors (actually, they are poisons) and among other things will cause blood-brain barriers and leaky gut phenomena, which will allow gut-derived toxins to infiltrate into places it should never be. Mold exposure (in apartment with mold, or inhaled into a lung) are believed to generate much more mycotoxins when stressed by EMFs, coupled with blood-brain-barrier porosity leads to neurological damage that mere 'detox' protocols prove insufficient to the task. Since you do not know if these are relevant to you, I would recommend trying a week of having zero such devices enabled around you as well as turning off the electrical breakers in your bedroom at night. This might actually help you fairly directly, or at least it is a free experiment with no negative consequences. You mentioned cognition challenges and that is a key indicator for EMF and/or Mold. If you can pinpoint the timeframe of the 'flare' origin, some of the sleuthing becomes easier.
Good luck with this long, long road. You would likely do better with a holistic doctor than with individual specialists. You are not alone -- way too many people have similar health collapses that look normal according to Western medicine standards. I will monitor this thread for a while if you want to engage on this topic further.