Obviously Rittenhouse still posed a deadly threat because he managed to kill two people.
Circular reasoning.
If you point a firearm at me, that is already a threat of deadly force, and the difference between that threat and me being dead is a fraction of a second. So a reasonable person would attempt to use deadly force when confronted with a firearm.
One of your problems is that you're trying to simplify the situation into "if this broad thing, then this narrow thing follows" whereas these determinations are based on the totality of the situation. There's a big difference between having a firearm pointed at you in an obviously threatening manner, or defensively when you act in a threatening manner, or haphazardly where the wielder does not have a good understanding of firearm safety, and so on. And there are going to be countless secondary considerations for any one concrete case. Reasonableness isn't a binary thing, it exists on a spectrum.
In any situation where someone did point a firearm at you however, regardless of whether in a threatening, defensive, or neglect manner, you would be more justified to shoot them within, or immediately following, the fraction of a second where you felt threatened than if you were to start chasing after them on foot. That's not to say that chasing after them on foot would never be justified. It certainly would be justified to pursue the Christchurch shooter, for one.
At this time there is no strong evidence that Kyle threateningly bared his weapon at Rosenbaum though.
If you point a firearm at me, I consider that a clear and imminent threat to me. I’d say Rosenbaum had plenty of reason to fear for his life, considering how he was shot fucking dead by Rittenhouse.
Circular, and very dumb. Next time you see someone open carrying an AR, why don't you go ahead and charge at them and grab for their weapon? The fact that you would end up ventilated isn't proof that you had to attack.
Once Rittenhouse - a kid running around pointing a rifle at people - established himself as a deadly threat by confronting people and waving his gun at them, his backing away does NOT serve to lessen the threat he poses to them because guns can (and did in this case) kill at long range.
All the people Kyle shot were at very short range.
I disagree with the assertion that Kyle was "running around pointing a rifle at people." And I wouldn't use the phrase "established himself as a deadly threat." I will say that some of the people chasing after Kyle, not knowing the details of his encounter with Rosenbaum, and only hearing about an active shooter, would be justified in trying to apprehend him, just as Kyle was justified in defending himself from being lynched (with members in the crowd shouting things like "cranium him") after exercising self defense against Rosenbaum. This is one of those instances where both sides can be justified. I don't know if I would extend that to Grosskreutz since Kyle told him he was going to the police. If anything, Grosskreutz is especially vile for helping to rally the mob to go after someone he knew was surrendering.
I see very little difference between going out and shooting someone, versus arming yourself and then putting yourself in a position that will ‘require’ you to use deadly force to defend yourself.
It all depends on motivation. If you're open carrying to act as a deterrent, then there is no similarity at all. Usually, you don't find yourself in a situation where you are "required" to use your weapon against unarmed individuals, because those individuals know better than to attack someone who is open carrying. That's the point of open carry. In the one-in-a-million chance you find yourself charged by a psychotic pedophile who was just discharged from a mental institution, you may have to use that weapon, and if you find yourself squared up against such a lunatic, going unarmed might end even more poorly.
If you go armed hoping that someone will give you the excuse to shoot them then that's premeditation. If you admit as much you lose your claim to self defense, which has happened to a few people acting "tacticool" to responding officers.
If Huber and Grosskreutz, and possibly Rosenblaum had gotten the upper hand on Rittenhouse and killed him, would they not even have been charged, or if they were charged, would they be acquitted on self-defense grounds? It does mean that yes, this is a situation where both sides could probably successfully argue self-defense.
Rosenbaum would be charged and would have no reasonable claim to self defense. He's also a repeat offender pedophile. The book would be thrown at him.
Grosskreutz would have a very, very, strong self defense claim if Kyle hadn't told him he was surrendering to the police. But because he did, it would be tough. Maybe not impossible though.
Huber would depend on how he killed Kyle. A single lucky blow to the head with the skateboard? Very strong. Repeatedly bashing Kyle's face in with skateboard until he expires? Much less strong. Disarming Kyle and shooting him? Depends on whether they were still struggling over the gun or not, whether Kyle was trying to regain possession, etc.
The issue in front of the jury will be what Rittenhouse reasonably believed at the time he shot. It’s possible that Rittenhouse can be found not guilty even if the victims were operating with the best of intentions.
Rosenbaum and Grosskreutz had the worst of intentions, but yes, Kyle's state of mind is (or at least should be) the determining factor. You may want to consider the fact that if Kyle had gone into Kenosha looking for an excuse to kill people, the mob that chased after him was a target rich environment. He only shot at people who were an imminent threat to him. He didn't mow down the mob indiscriminately. If he were looking for an excuse to kill people, he should have.