Crown installs on crooked walls
Newcomer to this forum and I read your distress call. Glad all turned out well. Being a trim carpenter for 24 years, I didn't find many walls that were true right angles (walls or ceilings.) The best advice is to learn about coping a joint. This eliminates the wall to wall angle problem. The square (butt) end slips inside the coped joint and can pivot plus or minus the 90 degrees. As for the ceiling, here is a secret I was taught by a Norwegian Master Craftsman years ago. Take a length of crown molding and cut sample inside/outside corners. Make them at least 6" long. Take the two pieces that fit the corner joint you're going to make and dry fit them for exact placement. Make a fine pencil mark below the pieces so when you return with the full length piece, you'll know it fits right. Alway cope one end and the other should be a butt joint. A good system to follow is to leave up the coped sample piece in place temporarily, with the full length piece in hand, you can slide the butt joint end into that corner (like having someone there to hold it in place) and then check the other "coped" end to fit over another sample trim piece (butt joint) on the other end.
Like I said, it's a system and it works very well if you follow it. If you're a right handed person, the cope end is on the right.