Sounds like he has tonsillitis. Did the clinic say that? I had tonsillitis often and always had a fever that high. I also had red spots on my tongue. All a part of the same infection.
I agree with Lynn M. If you feel that you need more info, call his pediatrician. There is nothing the ER can do that CVS can't do. ER would likely refer you to his pediatrician for follow up, anyway.