I suggest you read Peter Singer's book, "Animal Ethics", which goes into great detail on the ethics of consuming animal products within the framework of utilitarianism. Singer is often thought of as the father of veg*ism, so he's a great place to start. I don't know a great deal on the topics of environmental impact or health, but I think I can start some discussion on your questions.
"Can you rank animals by how bad eating them is?"
That depends on your personal views on the sanctity of life or lack thereof. This is a very easy question for me to answer - of course, for humans are animals and I place the value of their lives over others. Similarly I care much more for a pig than I do for an ant, but not so much that I disregard the ant entirely. It makes perfect sense to have a scale for which animals' lives have more worth than others, but I'm wary to do so in fear of being dishonest, since there's no way I'd put myself below top.
"Is it more ethical to eat wild animals because they have a good life before dying?"
I suppose, but it doesn't warrant discussion. This is merely a question of whether the life of an animal in its natural habitat is better than one on a factory farm with killing and eating them as a given. The answer there is obvious and I just reject the idea that killing and eating is necessary to begin with. I also believe a wild hunted human would be a more ethical meal than a factory farmed one, but I believe neither are acceptable. My views on factory farm and wild hunted animal flesh are roughly analogous to my ones on human flesh.
"The ethics of offsetting" (can I offset myself into ethically eating meat?)
The author of the article in question says here that they made some mistakes -
(12/30/16) In Vegetarianism For Meat-Eaters, part 2 suggested that donating to animal welfare charities could save 3 – 11 animal lives per dollar. Based on critiques like those in this essay, I now think those numbers are heavily exaggerated, maybe by several orders of magnitude. I don’t know what the right numbers are or whether the point is still somewhat valid.
That aside, I do not. In order to be ethical agents, we are obligated to do no harm. Regardless of what good you do in the world, you cannot act ethically and also intentionally do harm. Assuming imprisoning and killing animals is harmful, you cannot engage in it and consider yourself ethical in your treatment of animals if you believe that factory farming or meat at all is wrong.
These are of course my opinions, feel free to disagree with them or let me know with any questions or problems you spot.
"I suggest you read Peter Singer's book, "Animal Ethics", which goes into great detail on the ethics of consuming animal products within the framework of utilitarianism."
I guess you mean either "Animal Liberation" and "Practical Ethics"?
A related question came to my mind, but for the moment I will just add it to this thread and see whether people find it. So:
What is the best steelmanned case for eating animals you know, in particular the best ethical argument?
I find your answer to the question about wild animals very interesting. However, I am unsure what it implies. What would be the preferences of a deer itself if it could think of its own future as humans do? It would surely want to continue living in its natural habit, but would it want to die the way it can expect to do so in nature? Would it prefer that kind of death to being shot? (Or do you think none of these questions has ethical significance?) And actually, I don't know whether there is a literature on the ethics of cannibalism, but I would gues...
There are some standard answers to "an you rank animals by how bad eating them is?". Here is Brian Tomasik's ranking. The article goes into considerable detail and has a useful results table: How Much Direct Suffering is Caused by Different Animal Foods . Various people have proposed alternative ways to count, for example suffering/gram_protein, but this is the standard starting point.
Very interesting, though I don't fully understand it. For instance, extending the lifetime in the calculator always increases total suffering, which does not seem to make much sense to me.
If you haven't already you might also ask this question on the EA forum. It seems likely to me that it's more likely someone with a good answer to this would see this question over there.
Sadly I don't know of such a resource myself, but it seems like something that would be really useful. Most things giving arguments for veg*ism tend to lean at some point on a shared moral intuition that hurting the environment, killing animals, or animal suffering is bad, but it sounds like you want something more. For what it's worth, though, you can find stuff about all those questions spread around in different sources.
Thanks for the suggestion, I will consider it.
Moral intuition is often helpful, but not quite what I am searching for.
Ah my bad, fast typing forgot the right name. Animal Liberation is book which obviously specifically covers animal ethics while Practical Ethics has a wider breadth. I'd suggest Animal Liberation for your purposes
I am searching for a concise text that presents and optimally also discusses reasons for a vegetarian/vegan diet, including environmental and climate effects, health, but of course also ethics, and there are some ethical points I would be particularly interested in like "can you rank animals by how bad eating them is?", "is it more ethical to eat wild animals because they have a good life before dying?", "the ethics of offsetting" (the kind discussed in http://slatestarcodex.com/2015/09/23/vegetarianism-for-meat-eaters/) Optimally, this would be a kind of non-partisan text, but I guess for this topic this is hard to find because if someone writes about it, s/he usually explains her/his own reasons.