“You’re correct about the location of the ??”?. Sorry.”
No need to apologize.
I don’t think it’s more painful to have a feather plucked out than to have your head sliced off. I think what the Rema means is that the amount of benefit accrued by plucking a feather specifically while it is alive compared to that pain is not the same ratio as the benefit accrued by slicing off an animal’s head compared to that pain.
“I don’t believe we find anywhere in Shulchan Aruch a maalah in abstaining from meat because of achzarius”
True. But I would posit that it’s because food is a basic necessity and especially in earlier times, food options were limited. But for someone nowadays who can eat healthily and not mind not having meat, and feels compassion for animals, I can’t see how the Torah would have anything against that. Again though I reiterate that forcing vegetarianism on people as an important hashkafa might be different.