@Mels, sorry to hear you're going through all this. That really sucks.
I really can't comment on histamine reactions or food sensitivities or the causes of either, but my gall bladder is doing okay. I haven't had an attack since August. I take digestive enzymes with big meals (sometimes take extra if I know I'm going to be eating extra fat), and I also drink apple cider vinegar several times per week or sometimes every day if I feel like I need it. If I start feeling GB twinges the ACV seems to stop them. Interesting phenomenon. I picked up that tidbit on some blog while I was researching gall bladder and pancreas problems, and sight unseen, seems to work. ACV is reputed to help dissolve cholesterol stones in the GB, too, although it's hard to say if that's true.
I also drink chanca piedra tea. The herb chanca piedra is called "stone breaker" and is supposed to help dissolve kidney and gall stones.
I need to have another abdominal ultrasound to see where I'm at with this. If I still have stones I'm going to ask my doc to prescribe Actigall, which is supposed to help dissolve them, too.
All that said, I really don't even get twinges any more, thank heavens. I try to keep vinegar intake consistent (3x per week) regardless of symptoms, but will also drink it a couple hours after a heavy meal as a prophylactic, because I'm scared to death of having another attack, not because symptoms tell me I need it. Thankfully, my pancreas doesn't seem to be involved in this, and the bile ducts not inflamed, etc.
Will your doctors not at least prescribe an abdominal ultrasound? That would at least tell you the state of any stones you might have. Have you ever had an ultrasound?
Can you get your hands on some ACV more or less immediately, to give that a go? I don't know how that does with food sensitivities but I do know I'd probably try anything to get away from the gut pain of a GB or pancreas attack.