Sorry I did not read your post carefully enough regarding coconut oil and potatoes.
Well you wrote a whole novel about stuff going on now and failed to mention the elephant in the room that you had confirmed mercury poisoning (likely still have as cilantro is more of an anecdotally 'somewhat helpful' herb).
Before any of this, the first thing I usually recommend is take your body temp orally a few times a day and make sure you're 98.6 or higher, if not then you're hypothyroid, and address it. A lot of problems go away when body temp goes up.
Then another thing I always recommend is people get their macronutrient ratios down. You do this through experimentation with protein/fat/carbs-sugars. Go higher/lower in one and see what happens until you your body settles on something it likes.
So I'll explain some of my reasonings.
First, whenever I see someone say something like 'healthy foods aren't working for me' it usually means the foods aren't healthy. In ayurvedic medicine for example, aside from cooked garlic, or well cooked onions, all of these vegetables are known to be bad for vata dosha. Extremely sensitive people imo are usually vata dominant, and from your post it seems like you're a good fit. The raw fermented veggies are about the worst thing vata can eat, and sure enough your body is responding likewise. This is not a lectin issue, it's more like eating fundamentally wrong for your body type.
A good carb for vata would be pumpkin, sweet potato or squashes. Maybe you can do oats or starchy white rice.
Have you ever looked into peter d'adamo regarding lectins and blood type? I think his work is still best, and have not seen anyone as good as him with lectins.
I stand by your liver being in bad shape or else you would not be so reactive. How many flushes did you do, what happened, etc, etc.
Regarding lectins, I've been down those roads before. Yes, they are a thing, but some of the things I touched on are further upstream.
All of your veggie list are high sulfur foods. You can read Cutler's book on mercury to get the chemistry. Basically, assuming you are still mercury toxic (don't know yet but a decent guess) high sulfur foods just wind up moving mercury around causing more damage without excreting. You should definitely get a hair test to see what's going on.
For the time being you could try saunas to dump metals. Make sure you're hydrated with ample sodium, potassium, and staple electrolytes. Do you still have Amalgam fillings? Any root canals? Flu vaccine?
Actually I do knew a little about gunderson, I like his polyphenol supplement and recommendations. But there is this whole cloth of physicians turned naturalists who don't have enough background in natural medicine and then start making sweeping statements like 'cruciferous vegetables should be revered'.
Some basics are that you need fuel to burn. When I see someone limiting carbs, or can't do a lot of carbs due to various reasons, and they are not a good fit for keto, there will be problems. Sugar blues - meh. Actually diabetics can slowly titrate white Sugar to increase insulin sensitivity. Sugar is not the cause of the problem. Sensitivity to refined sweeteners = low mineral status. Do you take any supplemental minerals? I like bisglycinates. Zinc, chromium, vanadium, mag glycinate, calcium if tolerated, molybdenum can help the mcs/lectin type hypersensitivity, brewer's yeast is a good source of selenium.
You said veggies drenched in oil - yes very vata thing to say. Try sesame oil.
Olive and avocado oil are relatively low pufa compared to the seeds oils. You could try ghee, perhaps the tiny bit of casein/lactose in butter is throwing you off. You could also try some other saturated fats like shea, cacao butter, palm seed oil (only seed not fruit). I am not sold on pufa oils in any form.
White potatoes and sugar come from the Ray Peat playbook. White Sugar is problematic for some people, but it's not the devil that a lot of people in alternative medicine make it out to be. If you have problems with grains then White Sugar is a good sugar source. I did not read carefully enough that you don't do well with refined sugar. So I would test out all the sweet fruits instead and find which work.
All canaries' livers are plugged up. So I'll double down that your liver is not pumping bile well or much at all. If your stool is not dark brown and/or you exhibit other symptoms of bile stagnation, then you might want to look into getting deeper into liver function.
It's hard to know exactly which will help you from one post (that I did not read carefully enough - usually I do)
After a hair test and reading Cutler maybe there are some supplements that could help you like taurine or NAC.
If you must eat the goitrogen crucifers, cook them to death and add vata friendly spices, salt and fat, that will mitigate the damage they cause. Check your temps after eating crucifers to see if it goes down substantially - might indicate Iodine supplementation will help. Iodine is great, but I didn't mention it yet due to information overload.
Lectin info was available pre-2000 from D'adamo. None of the other lectin people impress me. Blood Type Diet is great for some people, really great. Him and is father, who did a lot of the pioneering work are OG!