I was a vegetarian for about three years in my early twenties. My then boyfriend was a strict vegan, and we only ate biological food from trusted sources. I also tried to avoid buying leather bags, boots etc.

I did it because I felt sorry to kill animals for food and leather. Your first argument wouldn't make me change my mind, and it's still not that convincing for me now to be honest, for the following reason: I believe that if we really stopped raising animals for food we would slowly have to turn to other raw sources for the rest of their applications. Materials are more flexible than we think. There can be many smart ways of substituting a raw material with another or synthesizing one with similar properties.

The reasons I stopped being a vegetarian were the following:

1. As my vegan boyfriend claimed, if you really care about animals, you cut off all animal products. Why is imprisonment, confinement and forceful impregnation of cows so that we can get their milk, for example, worse than just hunting and killing? The point is to end animal abuse, right? Is hunting an abuse, since the animal dies fast and you use its meat for eating instead of torturing it?
   I give him that.

2. Your third argument about plants experiencing pain. Plants want to survive too, plants feel pain too, and I remember reading an article about how plants warn each other of predators and they change their biochemistry to fight them off. So it doesn't really matter whether its animals or plants, you are still killing something. Since it's impossible to live just by photosynthesis, it was either my survival or the rest of life's.

3. Practical issues. Finding only vegan, biological food and in a great variety, (variety is key as I would be missing out on many readily available nutrients found in meat), is both extremely expensive and almost unavailable in my country. I don't think I could live a healthy life under these circumstances.

I still feel sorry for eating animals and especially having a pet I often feel hypocritical for the discrimination. At this point, however, I'm more likely to set my pet free back in its nature than become a vegetarian again. Life is harsh indeed, but I guess you either adapt or perish.