Congratulations! I'm glad this worked out so well!
Chicks that are cared for by a broody hen rarely get pasty butt. I think it's associated more with shipping stress and/or chicks getting too hot or cold.
The hen won't reject the chicks if you pick them up, although she won't like it...
My advice is totally different from what other folks have recommended, but here goes.
You mentioned that she has already been broody for several weeks and is noticeably smaller than she used to be. A broody hen loses approximately 20% of her body weight during a 3-week incubation period, as...