drywall celling

Hi all - I've searched the forum and I think I know what happened to my bathroom ceiling, but before I fix it I want to get confirmation I redid a 50-yr-old bathroom this past year. The original BR had 4-inch tile in the shower area, on the ceiling as well as walls. I took down all the tile and retiled only the walls of the shower (normal 5' tub/shower area) and plastered over the concrete/cement ceiling and painted it with ben moore ceiling paint and called it a day. It started peeling a month or so ago, and it looks like an area that I had skimcoated joint compound over the ceiling cement peeled away and a good-sized - maybe 6 or 8 inches - is curled back and there are some other cracks developing elsewhere. The skimcoat in that area is about 1/16 inch, give or take. So - I'll chip it all back to where it adheres (if anywhere), and re-skimcoat. Is there something better to use there than joint compound? Rather than go back to Ben Moore, I should use Zinnser's Perma White for the ceiling. Is there something else I should do as well? thanks - Mark

I have an open space upstairs that I will need to enclose for a couple of years. New carpet is being installed throughout the upstairs prior to the new wall and I will need to minimize (eliminate) any damage to the carpet. The wall will enclose the area making it a bedroom. There is no need for any electrical in the new wall. I am trying to figure out the best way to complete this to save the sanity of the family and eliminate the need for kids to share a room. When the oldest moves out I want to remove the wall and have the space returned to the current state. Any suggestions are appreciated.