I’ve never used a glucose spray–I’ve always had either tablets or gels. In a seizure situation, the gel tubes can be squirted into his mouth–it may get messy and he may spit half of it out all over himself, but getting anything in there is better than nothing. I would suggest his friends do that AND call 911. Do not expect the gel to work on its own–still call for help.
As for a medical ID, sure you can insist that he wear it while away. It’s not an unreasonable request, but just know that once he’s away from you he may take it off anyway. Personally, I’ve never worn a medical ID in my 32 years of T1. However, I am open about my diabetes and everyone around me knows that I have it—family, friends, coworkers, etc. If he’s not going to wear an ID, stress to his friends that it’s important to tell any first responders that he has type 1 diabetes. Is he on a pump? That’s kind of a dead giveaway that you have diabetes too.
I do keep a medical ID card in my wallet behind my driver’s license so that it can be easily found if I am ever alone.