A few crucial points you are missing:

There's absolutely no legal obligation for the cops to answer any of your questions. Feel free to ask them anything you want, but they don't need to answer. Further, they can lie to you about why they pulled you over. I've seen videos where they were stopping an armed violent offender known for resisting arrest for their bigger crimes. So the cop pulls them over and wants to keep them calm so they only tell them something like seat belt or light violation. Then get them out of the car so they can't reach for hidden weapons. And YES there are plenty of videos of people reacting innocently asking the same questions this guy asked only to suddenly pull a gun or something.

I'm sure all states have some law that requires you show your license when pulled over (mine definitely does) . Even for flimsy victimless traffic violations. Even if you absolutely are wearing your seat belt and had video evidence to corroborate, you would still need to show your license if pulled over for a seat belt violation. It doesn't matter that you are innocent. The arguments you'd make on the side of the road are the exact same ones guilty people make. They'll swear up and down they were wearing their seat belt knowing they weren't. Nothing differentiates them from the innocent on the side of the road.

You keep harping about it not truly being inclement weather, but that doesn't matter. Even without the seat belt issue included, they are legally allowed to come up with RAS after the stop. That's one I personally think is utter bullshit but it doesn't change the fact it's legal. After all of this if it turns out he wasn't guilty of the other infractions but they figured out his registration was expired, they can just swap the citation to that even if that wasn't considered until after the stop was done.

This is not supposed to come off as defending cops. I'm all for legally resisting as much as you can, but this wasn't the case here. This was one to fight later in court. This doesn't further the cause of police accountability. This just sets it back and is one more example of the general public being woefully ignorant of the law that strengthens police resistance to positive change.

I linked to the full bodycam video, the officer clearly says that there were two reasons for the stop: Headlights and seat belt.

Your video has the AI voice claiming that failing to give a Miranda warning before opening the door is a "clear 4th amendment red flag." That's a load of steaming crap. Moving on to the actual issue at hand, the charge there was for unlawful carrying of a weapon. The judge's decision is that by the officer randomly opening the door of the guy's vehicle, and then seeing the weapon, that means it was an unlawful search (it was "in plain view" according to the officer / prosecutor, but the judge says it wasn't in plain view until you opened the door). That has literally nothing at all to do with the initial stop being unconstitutional, or failure to ID or anything. It's just to do with how the cop found the gun.

Do you have one where the person failed to ID on a traffic stop, and their lawyer was able to make the argument that the initial stop was improper, and so they didn't have to, and it worked? I feel like those would be super-easy to find, if that argument ever worked, since it is very commonly what people say while they are refusing to ID, and so if their lawyers were able to make it work we would have examples of it working.