Hi, Robyn. You can try to restore your original ceiling but I doubt that you will be successful. The metal used in tin ceilings is very thin and any rust at all is a sign that rust has made it even thinner. I would test a small area using Peel Away for 24 to 48 hours and then a stripping pad to remove any remaining stripper/paint goo. When you have all the goo off, neutralize the Peel Away with white cider vinegar and then rinse with water.
Since you will be working overhead, this is also very dangerous. Don't even think about doing anything with these chemicals without rubber gloves, goggles over your eyes and an old hat. Have a bucket of water close by in case ANY of the stripper gets on you. You might try "painting" the Peel Away on the release paper and applying that from the bottom. Personally, I would replace the tin. This will be expensive but the difficulty and risk of stripping could make stripping even more expensive. There are ads for new tin ceiling material in home improvement and restoration magazines. Even replacing a tin ceiling is difficult and dangerous and probably best left to the pros.