This is typical of the thoughtless "reasoning" one hears from gun control opponents. First, nowhere in the 2d Amd. does it state the amendment "exists to guarantee the people of the united states retain the capability to wage war against the government." You made that part up on your own, and thoughtlessly so.
No - our constitution does not establish a quasi-sovereign state. As a sovereign nation, the USA rules supreme and it's citizens are subordinate to its laws within the bounds of its fundamental constitutional safeguards (civil liberties - which establish limits on what government can do; and civil rights - which establish guidelines for what government must do.) Nothing in the 2d Amd. permits citizens to violate the constitution.
You're one of those low-effort thinkers that believes something in the Const. gives you an unqualified right to bear arms. It does not.
Question: should any random, sane, God fearing white Christian be permitted to build and possess a nuclear weapon in his home (kept safely behind his white picket fence)? Answer: F*** no.
Why? the obvious risks of harm and threat to our national security and general welfare are too great to permit these kinds of arms from getting into unqualified, unregulated hands. Even the most crazy nut-job opponents of gun control can recognize that the "right to bear arms" is not an unqualified right to bear just any old arms. Those who disagree with this point are probably not qualified to own any arms of any type or degree.
Once you admit the right is highly qualified (not any arm, just some, and not for purposes of over throwing the government - which would be a clear rejection and violation of our constitution as a matter of both time and logic), you can start to make some intellectual progress. Until then, you're one of those people that are best described by the saying "like a broken tooth, so sits a proverb in the mouth of a fool."
A conversation about gun control isn't about our "right to bear arms," but rather, it's about what it means to permit certain citizens to bear certain arms in a civil, peaceful society. In this context, your test: "what is an acceptable loss?" might bear some fruit - because we aren't comparing the loss of human life to some imaginary loss of a fundamental right. In that context, your test is still relevant - it's just doesn't conflate or confuse the choice we must make with something illogical, non-nonsensical or unsustainable in practice.
Questions regarding what's at risk, what can be done to hedge against that risk or prevent it, what are the costs/benefits to society for doing so, etc., do not attack a fundamental right. They explore societal threats that need and deserve rich debate and conversation. BUT, before we can have that conversation in a productive fashion, we have to get smarter about what we are talking about -- and it's not the vitiation of a fundamental and unqualified "right to bear arms."