If you're afraid of surly teens on skateboards it might be time to put away the gun and get yourself a gym membership.
Sorry, wrong attitude. If that was a cure, then Colt would never have invented handguns, right?
God made men, Colt made them equal, etc etc.
You can't buff out and make up a 150 pound difference or 18 inch cut in height. You can't always overcome a handicapping injury that leaves you less mobile than your adversay. You can't always overcome the gender disparity that makes you 75% as capable as your adversary. That last fact is exactly why smart women are arming themselves, and they are helping our 2A rights by doing so.
So lets cut the attitude. I'm well aware of it's source, played the game for years, but at 61, with a titanium rod in one leg, 5'5", and a bad back, going to the gym will NEVER make up enough difference.
The OP posted some credible scenarios and they happen repeatedly in daily life entirely because of that same "Well, you just need to go work out more" attitude. What is really being discussed is "Monkey Dancing." It's the verbal and physical posturing that goes on to determine male heirarchy, who has dominance in a situation. Obviously, the "offenders" in the cases presented question their place, and are attempting to elevate themselves over you.
Why? 75% or more are no longer raised in a household with a dominant male, so they have no one to measure against and have to inflict their methods on the general public.
We now see polite society attempting gangbanger sociology just to fit it, all because they don't know how to do it better and didn't get tossed by Dad until he could say (with pride) Hey dude, you made it.
So, as the OP has pretty well explained, they go out with no intent, but do see a target of opportunity and do the menacing FIRST. That is what creates the situation. Unfortunately, without a body cam to record it, what you have are punk kids pushing the envelope of social behavior. Actual intent to kill isn't often the point, it's just putting YOU in YOUR place, so to speak.
Escalating to deadly force is just going to full triple dog dare and will be seen in a court of law as too much too soon.
In most of those cases verbal sparring is the solution. Not a firearm. Leave it concealed, it would be a tactical mistake to show your hand too soon. The better solution is to approach it by being the adult - which they aren't - and if something needs to be said, it has to be with an attitude of dealing with something that happens all the time and the outcome isn't threatening at all. More like they are just children playing around, verbally brush it off.
"Go work out in a gym?" Not so much, you get the same crap there as on the street, in an environment that is even more prone to engaging the monkey dance. In that regard it might be relevant, as putting up with even more narcissistic muscle boys would certainly be an education.
Better a few years of bare hand combatives in a discipline with no deliberately imposed heirarchy, just an atmosphere of mutual respect, which is what life is supposed to be like.