One thing I have been wondering about as I have reading this thread is whether something in the kitchen is cross-contaminated with your allergens? Examples would include the cutting board, kitchen drawers, the refrigerator door, and refrigerator doors. Especially the cutting board. Maybe those few foods you can eat safely are the ones that don't come into contact with the cross-contaminated surface.
Another thing that jumped out at me with the banana and some of the other positive blood tests is latex allergy. Any possibility you have something in your kitchen made out of latex - like latex gloves?