"Does anyone here actually know what the framers of the Constitution really meant when they spoke of militias and bearing arms?"

I think in general their biggest fear is that America would become like Europe- or countless other States throughout history. So, militias and bearing arms was the last ditch defense against tyranny. But more importantly by having arms, hopeful that would be enough prevent getting to the point of needing the last ditch defense against tyranny.

In term of comparing horrible evils: the Holocaust and Rwanda- the founders would have probably preferred Rwanda.

The principle is quite simple, America was to be a republic. By which is meant that sovereignty flowed from the people- and the people were citizens of America which owned land. And the citizen had not only the right but duty to protect their land. So now the question could be that with the public paying for a police forces, and with the public paying for a military, do Americans still need to defend their individual property and the nation itself. That might make a fine debate and maybe we could have it, and maybe we could decide to change the constitution.
But in the meantime, it seems to me that federal law should allow all citizen to posses modern weapons used to in modern warfare and it also seems to me that a individual State could possible restrict weapon ownership if the people of the State wish to do so. And it's for the courts to decide how to resolve any conflict that my arise without changing what is decreed by the Federal constitution.