These are not uncommon reactions following tonsil and adenoid surgery. The antibiotics are very important to control present or possible infection. The pain will slowly go away. If your son will not tolerate the hydrocodone, try Tylenol
you could also try tylenol rectally to help the pain.....wait about a half hour before you try to give him anything to drink........ try popsicles, jello....usually the pain and discomfort returns around the 4-5th day after surgery ....my kids had theirs done and it is normal......but if his fever goes up he could have an infection or a little atelectasis of his lung.....this is just where his lung isnt quite expanded as it should be....sometimes it follows surgery of any kind....keep in touch with his surgeon.......good lluck
If his temp goes much higher I'd for sure call the doc again. This poor little guy sounds miserable. You've got to make sure he doesn't have a post op infection.
Keep bugging the doctor. Squeaky wheels get results.