this site pandagon does a video recap/analysis each week that is pretty good (from an explicitly feminist perspective, fwiw)
http://pandagon.net/index.php/site/c...en-the-phantom
their take on the screentest is that a) Don see's that she is not a natural talent and b) he sees her expressions in the abstract and realizes that what he fell for originally was in part an act...
i also agree that Don isn't just going to return to his swinging ways, but their relationship has fundamentally changed and is going to fall apart, imo...no clue where Don goes from there