In my experience....moving them to a completely new area can break them of their broodiness. I think you are fine to divide the eggs among each hen as long as they are all expected to hatch at the same time.

I also think you should do what you need to do for the health of your flock. Yes, if chicks are taken away from the mother, she may become distressed, but I wouldn't apply human emotion onto birds too much. Just do what you think/know to be best for your birds....if you are saying you don't have enough room, then it is right that you make other arrangements.

Those temps are just fine... if not down right optimal.

Wait until after the hatch if you have to move them. Dion is right, moving them can make them abandon their nest. I've never had luck with doing that, especially with guinea fowl, though you are talking about chickens. As long as you let your hens brood the chicks, they should be okay and keep them warm with their body heat and mama hen's feathers, though it's usually not a great idea to go too far out of the 'spring chicken' season with birds, ma nature knows best.

Problem with letting 3 hens brood their own chicks in the same area is, the hens will usually fight with each other about who's going to get the food and water for their babies. I don't know how many eggs they're covering, but if they don't have a huge hatch you may want to select the biggest mother (or best mother) and let them watch all the other chickies alone, no other hens around.

I wouldn't worry about the hens being depressed about their chicks being away, chickens aren't like humans, after a few days they won't even bother to worry about it. If your brain was the same size as a chicken, you probably wouldn't worry about too much either, right? ; )

Oh, also don't move the eggs from one hen to another, that can wreak havoc.