Dante, from your described reactions, it sounds like many different foods are causing you difficulty. Perhaps a doctor's guidance would help. Dr. McDougal takes patients. He's in northern california. Dr. Klaper is also in cali. And Barnard is near D.C. Dr. Esselstyn is in Ohio. If you're near one of them, perhaps you could speak to them. If not, they might be able to recommend someone near you. It seems worth a call. I'm sorry to hear of your food troubles.
On cruelty:
There were a few responses to the idea of cruelty along the lines: that's life; it's not so bad; and as long as its humane its ok. For the sake of discussion, let's say that's true.
The word cruelty here does not refer to humanely or even quickly dispatching a creature in order to live. Cruelty refers to causing the intense or extended suffering of another when it could be mitigated or avoided.
Often individuals feel they could raise an animal in comfortable, clean conditions and dispatch it humanely. If so, there is a way to scale it to market levels. The thought is that for some additional cost, humane practice is achievable.
Author Jonathan S. Foer asked the same question, researched it in detail, and wrote about it in his book Eating Animals. Although the name sounds like it has predisposed view, don't be mislead: the book is quite open front to back. In fact, the author doesn't choose veganism at the end of his journey. I did.
It's an interesting read which explores this "premium" part of the animal industries. Organic, free-range, humane...etc. I was surprised and saddened by what I read, and chose to opt out of animal products.
Ok well obviously halal meat is barbaric, you can just see that in the definition. But as long as you just head to your local farmers market where you can actually talk to the people themselves, I guarantee you'll be getting something ethically raised and at least relatively so slaughtered.
Yikes. This is bordering on Islamophobia. I prefer inclusive and friendly. I'm curious why you feel Halal meat is inhumane? Is it that the mental image of this slaughter method is gruesome? I wonder what method seems humane to you?
Some investigation into humane slaughter might interest you. I searched extensively. It turns out people are studying this on a neurological level.
Unfortunately, I did not find humane practices in use. Markets often force efficiency and scale at the expense of other ideals like quality, fairness, etc. Sadly cruelty is faster/cheaper. Read about it long enough and you'll notice increasing cruely correlates with increasing efficiency.
Consider the case of male chicks: they don't lay eggs. There is no profit to be made from them. Read about what egg farmers do with male chicks when they hatch, see what you think. Study the issues of cruely, slaughter, farming. See if what you find meets your expectations. When I looked into it; there were no methods I could accept. Your mileage may vary.
There was also one idea expressed that your body needs certain things available only in animal products. This is untrue; what materials in particular do you have in mind?
Per my understanding, the only material humans need that we can't get in sufficient quantity from (whole, unprocessed) plants is vitamin B12. Vegans supplement B12 gathered from plant sources in a concentrated quantities. FWIW, the animal foods rich in B12 are not always popular (like mackerel, or liver). The B12 issue is not limited to veganism.
