Hi JAM's Mom and Welcome
If you still have trouble getting a diagnoses for your son from a qualified doctor, depending on your son's feelings, maybe you could video tape his tics. By doing this the doctor would be able to see the tics that you are describing. However, if your son refuses to be video taped for this purpose I wouldn't push it.
The one thing that stands out at me is that you said your son has severe leg jerking when he eats ice cream. I would consider removing dairy from your son's diet to see if dairy is a tic trigger for him. Dairy is a large tic trigger for me. There are many tic triggers that can be found here:
http://www.latitudes.org/articles/finding_triggers.htm
I hope this helps. Also if you get a diagnoses and the doctor gives you a med for your son to try, just remember that there are also med free options to try that doctors may not educate you about. I suggest doing your own research to find the best plan for your son.
Carolyn