You should have no problems with him inside. I've known people with parrots who use air purifiers in bird rooms, and they do work. If you think you need one, just read reviews at Amazon for air purifiers, and type in the review search box "parrots" or "birds", etc., to see what's recommended and what's not.
We have been discussing in another thread birds that shun or kill weaker birds of their own kind, but I've never heard of pigeons killing each other. Does that happen?
I tried feeding mine all those normal pigeon things, too, but she only would eat millet! Which, of course, is so strange with a pigeon! I've had pigeons inside before and they always ate typical pigeon grains. I wonder if it's a sign that there is something wrong with a pigeon that only wants millet? As I said, mine got her leg caught up in seaweed on the beach, when she was still a slim young pigeon, which was sort of strange. Maybe there was something wrong with her before that happened. Or maybe she had the bad leg before getting caught in the seaweed.

h, what a pretty boy!