I'm allergic to all of the same things as you, but I've found that I don't react to oranges, so I can still get a good amount of vitamin C and some extra potassium from them. (Read up on latex-fruit syndrome). Potatoes may technically be a nightshade, but I get no reaction from them, whereas tomatoes, peppers etc. will make me itchy a few hours after eating them. Good quality meat of any species works fine for me, but too much tropomyosin from seafood tends to cause a slight reaction, with shellfish being far more dramatic than fish. I've been eating pounds of sole and cod lately without issue.

Roasted treenuts seem to be fine as the allergenic proteins are denatured. Egg whites get me, but egg yolks cause no reaction and have all of the most important nutrients anyway.

You're gonna want at least 1/4 lb of liver per week as per usual.

I'd recommend supplementing with 1/4 tsp of calcium citrate and 200mg of magnesium glycinate just in case. Also salt a few meals if you don't already.

If you construct meals consisting of 1 piece of fruit you don't react to, 1 lb of correctly-fed/wild meat of your choice (that you rotate) and 1 tuber, you will have a very nutritious diet without any reactions.

1. I don't know.

2. You mentioned gluten, but you didn't mention non-gluten-containing grains like sorghum, etc. I'd probably eliminate all grains to be safe.

3. Uncured pork seems to be somewhat inflammatory, and causes an aggregation of platelets in the blood, or something like that. There was something about that in a recent Wise Traditions article. And chicken tends to be relatively high in Omega-6 fats, at least if it's not pastured. So rudiments like beef, bison, lamb may well be better.

4. If I had to choose one supplement, it would be fermented cod liver oil (perhaps the blend with high-vitamin butter oil as well). I think the line between "supplements" and "food" is rather blurry, so it's hard to answer this question in the abstract. I don't see anything wrong with taking vitamin D3, though, if you're not getting enough sunlight to meet your vitamin D needs that way.

5. I don't see why organ meats would be a problem. About cabbage and vinegar, I don't know. If you're avoiding FODMAPs, you'd want to avoid unfermented cabbage and apples, etc. But when cabbage becomes sauerkraut and apples (etc.) become vinegar, I'm not sure to what extent the FODMAPs are eliminated. Good question.

If you're allergic/intolerant to dairy I would cut out the ghee for the duration of your elimination diet, for the reason that it's better to be safe than have to redo the whole 2 months.

Otherwise, your plan sounds almost exactly what I'm doing. I eat well-cooked greens, grass-fed ground beef, and either sweet potato or butternut squash for breakfast and dinner, and a salad with fish for lunch with coconut oil and apple cider vinegar for dressing. It was making me have more omega-3 than omega-6, so I've added in some chicken meat once a week. I've also been eating beef and chicken stocks, kombucha, water kefir, and home made sauerkraut. When I can I eat liver or kidney (beef if I can, otherwise I settle for chicken), maybe a couple times a month. And I found a chocolate I can eat with no reaction, so I eat that about once every week or two.

If you're at all sensitive to gluten, I'd be careful to make sure any vinegar you use or tea you drink it gluten-free. And watch out for herbs, too, as they can be cross-contaminated.

As for macronutrients, I find that the above plan does well for me except I'm lower in thiamin and folate than the software suggests.

Unfortunately I don't have experience on whether apple cider vinegar or sauerkraut cause FODMAP problems. More importantly, though, is whether they cause FODMAPS problems in you... so maybe you can eliminate them at first, and then see if you can add them back in after a few weeks.

In my experience salmon caused similar problems to shellfish, but tuna, mackerel sardines didn't. But then in my experience my allergy to any of them disappeared when I went Paleo. I doubt you'll see anything signficant from cutting out pork and chicken, though you can try if you like. I'd say including organ meat would be important both to make things interesting and cover nutritional bases - similarly make some use of the bones. That ought to be sufficient - if you have to eliminate those then it may not be worth doing. I don't really understand the low-reward part. I'm not aware of that having been related to allergies nor does your plan seem particularly low reward.

make sure you are enough fat, eating fatty cuts of meat, i would suggest keeping at least egg yolks as park of your diet......... http://www.drlwilson.com/articles/HEALING%20LIFESTYLE.htm

For question 1, being allergic to shellfish doesn't make you allergic to fish, or vice versa, especially if your allergies are anaphylactic (not just "irritation", if it is might just be the iodine). For peace of mind, I would book an appointment for allergy tests (with an ALLERGIST not a naturopath, no offense any among us). You could find that you are allergic to some shellfish but not others- my boyfriend can eat prawns, shrimp, oysters, canned tuna, and muscles, but if he eats any other fish (salmon, halibut, sole, trout, cod, lingcod) or scallops, he immediately starts swelling up and we have to get the epi-pen ready. If you are unclear about what you are or are not allergic too, you should go get testing first and foremost.