Yeah, you're screwed. Drive carefully and safely to not trigger the stop in the first place. That's what I would do.
You are also absolutely right - even some of the so-called "pro 2A" officers think that the police should be the only ones carrying.
Anywhere else, I'd agree with you, but this is NJ. Sure, there are many pro-gun or simply intelligent, sensible officers. But there are plenty here that think that only they should carry guns and will charge you even if the case is flimsy.
I don't know, but most firearms violations in NJ are a felony. Also, the 450 feet requirement sounds like statewide hunting regulations so I suspect it may be a state law redundantly added into local law. I don't know, but I also don't want to find out the hard way.