This isn't going to answer your questions, but I finally let mine out for a while yesterday evening. Before I had only taken a few at a time, and twice led them across the yard to the run before I moved it.
I might feel safer doing this part-time. Not everyone came out (funny, the banties were less interested than the standards, only one banty came out of the coop/run) and I had to keep shooing them away from a large brush pile that might have snakes, and I had to keep an eye on the kitten who refuses to be put away from the chickens. (Can you say "new playmates!" ... I don't trust that cat though!) AND I had to chase the ducks off with a rake. Kupo pulled some feathers from one of my babies within seconds of them coming out of the run!
Didn't see any hawks (not sure I could've done anything in time if I had) but I watched. And it took me a while to get them all back in ... they go in the coop easily, but returning from the yard was different, apparently. They were having TOO much fun!
I was a little nervous trying to keep up with so many chicks heading in different directions, and so many sources of danger (though most of the dangers were very low-key). Hehe, two of the chicks seemed to think the duck-pool might be interesting ... don't know WHY they thought that!
Two sides ... if you limit the exposure, perhaps you limit the possible dangers. Then again, with limited exposure, perhaps you lengthen the learning curve and it might take longer or might be less effective for them to learn to be safer out there.
Like I said, I know I'm not answering your questions. I'm just learning myself.
I do wish more of them would come when I call. Most do, but not all. And even though they come, that doesn't mean they walk into the run afterwards.
trish