no she still has to eat, they cover them with the down lining they put in the nest and they are just fine for an hour or two.
I always advise brooding in a closed brooder, it's much safer there are many things even in baby proofed pens that can cause problems with ducklings.
As for coming out of the box, they are fine, the naturally do it, hit any thing on the way down and run off just fine, they are very limber and flexible at hatch just for that reason. Some in the wild will fall 40+ feet and hit the ground below just fine. As for distance, they dont, they just get to the opening and bail out straight down.
Good luck with them.
I'm not 100% sure on the xtact current rules on housing, but I know purposful release is illegal. If pinioned you may get by with it on a personal pond, but I believe they do even still have to be inside some form of pen. or fence. Will check into that and get back on it.