Following the suggestions here, I made a bracket from Aluminum 'L' stock. Used it to push the wall into correct alignment and attached it to ceiling.
Now we need a way to trim the junction between the wall and the ceiling. So we fashioned a template,
glued up a blank using 'scarfed' miter joints.
Cut, finished and installed the trim piece
We're pretty happy with how it turned out. Thanks for all the help and suggestions.