Here's my analysis...
... IMHO, I'm not a lawyer, nor do I play on on TV.
Brandishing, disorderly conduct, and obstructing an officer.
Brandishing: weapon was slung, this is not brandishing.
Disorderly conduct: OC in and by itself is not disorderly.
Obstructing: presenting ID is not required, especially without RAS.
If he was stopped just for OC, he would have a slam dunk.
However the LEO(s) will state that it was not just OC, but the fact that he looked underage to carry a weapon.
It is illegal for a minor to possess or carry a rifle or handgun (exceptions, hunting or at the range, etc)
His appearance of looking underage is an element of the crime, thus giving the LEO(s) RAS to stop.
The Terry stop is to investigate if he is "of age" to carry, therefore he should have presented ID just for age verification (but he still is not required to show ID).
So...
Brandishing: weapon was slung, this is not brandishing.
Disorderly conduct: OC in and by itself is not disorderly.
Obstructing: LEO(s) had RAS for his age, but he still does not have to present ID, but then he can be arrested, taken downtown & processed until his age is confirmed legal to carry. Once his age is verified through other means and found to be 18+, then he should have had the underage carrying arrest dropped & be released with his property.
I feel that ALL the charges should be dropped, but I am worried that depending on the judge, prosecutor, and how well his defense lawyer does on the not required to ID presidents (with the fact he didn't just shut up under "taking the 5th" and wanted to debate), he might still loose the Obstructing an Officer charge.
I wish him luck