It is a pity that Barbara's soot explosion isn't an actual power. Otherwise we would get to see John call it something like the Barbara Blast or Barbara Bakuretsu.
Also, how long was Christopher in charge of the children's building? Everyone in the flashbacks seems to have dropped at least 5 years.
The success of their time as star bearers may be reason behind the rapid rise of Edward's trio within the adults' building and Edward's subsequent promotion to manager. After they and Christopher were invited, it probably became apparent that the success of that time was due to Christopher's debutant class, not the efforts of Thomas or some other manager.
The details of Christopher's ghost story match what happened to Rosemary during the first ghost incident (clingers combining to form an entity that drags someone's body). Every other time we've see clingers attack faces, they have followed the simple pattern of jump on someone's face, then entering their mouth. I'm guessing that part of the first incident was probably staged.