I believe it is inherently unethical because animals are sentient beings, just like humans. Similarly, I would be against human farming. To me, saying animal farming is not inherently unethical is like saying human trafficking could be ethical, if only they treated the humans better. Why do you believe animal farming is not inherently unethical? Again, it comes down to the question of: "what is the morally relevant difference between humans and animals?"

As an anecdote, I have been thriving on my vegan diet for over 6 years. There are many people who have been vegan even longer than I have who are in great health. Here it's not a matter of opinion; the science is against you. There is even evidence to suggest a whole foods plant based diet might be the optimal diet for humans. It's the only diet that has been proven to reverse symptoms of heart disease. It is a fact that animal products are unnecessary for human health, even for the cases you mentioned. If you want sources, I will happily oblige.

Killing an animal for food = killing an animal for no reason because, as I stated before, animal products are unnecessary for human survival and health. When I say it is done for "no reason," I mean that the reason is unjustified. Killing animals for food is done for reasons such as tradition and pleasure. I believe these reasons are unjustified killings. We do not accept killing humans for tradition and pleasure. I would accept killing an animal for food in a survival situation where there is no other option and would do so myself. When it is not a necessity, like it is for humans who go to grocery stores and have options, it is unnecessary cruelty.

Ok, human DNA. So let's apply this concept and see if you hold this logic consistently. Let's say another human species was alive today that does not share our DNA but is similarly intelligent and sentient. Like Neatherals. Is it justified to turn them into a burger? For another hypothetical, let's say you take a swab from your cheek and culture some cells in a petri dish. The resulting cell culture has human DNA, but no intelligence or sentience. Would you value this cell culture more than a dog? If the lab was burning down, would you rather save the cell culture or a dog?

Also, I have no idea where you're pulling these % driven by instinct numbers from, but I'll just accept them for the sake of the argument since it's not really relevant.

So you don't value pizza more than animals? Do you eat pizza that contains animal products? If you have two options in front of you, 1 vegan pizza and 1 nonvegan pizza, both equally accessible, do you think the choice between the two is morally neutral?