everyone has the right to kill whomever they wish or think is a threat or has something they want
LOL...no, that's as laughable a stretch as thinking that "bear arms" means to carry them.
You keep trying to read a description from the name. It's like trying to deconstruct "Alfred Spangler" into, "A Red span". Yeah, the words are there, but a name is representation, a symbol, not definition, and what a name represents often has little connection to the words that make up the name.
Why would the same people use "bear arms" in one document to mean what everyone since Aristotle has meant by the phrase, but in another mean, "it means you can carry them, but not actually pull the trigger"? The founding fathers had, in living memory, personally exercised their individual right to bear arms in the common sense of the phrase. Not, "to carry them but not pull the trigger", not, "to transport them", but, "to take them up and use them, killing and wounding people in the process", and they did it against the rightful government of their lands. They KNEW exactly what that right was. They had lived it, exercised it, and were only writing a constitution because they had done so.
The founding fathers would have been deeply offended to hear you describe their exercise of that right, their revolution, as, "kill[ing] whomever they wish or think is a threat or has something they want." I'm a bit offended that you think of them in those terms myself.
The right, as they saw it, was integral to the natural rights of free men. Which means it was something akin to (but more extensive than) our current conception of the right to self defense. They were within their rights to bear arms against the king because the king was doing them identifiable harm. They were not within their rights to bear arms against a farmer with better land because the farmer wasn't harming them, even if the farmer had it better than they did.
And they knew that the people, in other words you and me, is kept in check by different forces than a government. They required an act of congress for the GOVERNMENT to call forth the Militia. Given their general trust of government exercise of power, why is that surprising to you? The government always requires extra checks and oversight because government concentrates power. It takes an act of congress for the government to do things you are fully in your right to do this very minute with no oversight whatsoever, because the government can coerce where you and I can only discuss and trade.
I won't claim to know the full breadth of whatever the founding fathers were naming when they named that right. I suspect, based on alternate wordings and arguments from the day that there was a fair amount of disagreement at the time and they named the right instead of using the sort of wording found in most of the BoR very specifically to punt the issue on to succeeding generations. I'm not even sure it's relevant what they thought, except that they were smart people and their views certainly carry weight even today. The important thing today is to define what we mean, a consensus of what that right is today, that is as broad and generally beneficial as possible.
But, to be somewhat fair to your point of view... the founding fathers were known to duel...pistols at dawn sort of duel. So yeah, they saw themselves as having a certain right to commit what, if it happened today, would be considered murder, within very clear and well known limits.