For the meantime, have you tried Feliway and Rescue Remedy to calm him while he's in the room.

A bit late now, but I put plastic carpet runner under the doorways. Cut out to fit through the door jambs.
But if you want to keep your carpet from getting worse, it might help.

How mean are the girls to him?
Are they running toward him to attack him?
If no one is getting injured, they might be able to adapt, within a few days of nastiness.