Do you have a humidifier? A humidifier in his room and Vicks works well for my son. Does he also have a fever? If he has a fever also give him Tylenol or Motrin to bring it down.
a cool mist humidifier is an excellent idea. prop the head of his mattress a little this will help with the mucus in his system and may help him from vomiting also try to reduce milk products. until he can get in. not sure what the rash is, so I can't say what you can do for that
good luck