I would love to toss in my two cents, but I can't really do so as thoroughly as I'd like because reasons time. But I can offer a couple views.
I believe that yes, a natural human government will inevitably deteriorate towards corruption. My preferred solution would be a... deiarchy? Basically, rule by God. But that won't happen until the Second Coming, and I don't know when that will happen, so for now I'll settle for a republic.... so long as that republic is run by honest, good men. Which leads us back to point one, unfortunately.
By the way, I do wholeheartedly support the Constitution (I'd consider myself a Constitutionalist). I believe it is a divinely inspired document, but that it was meant for a religious, moral society. Which we're drifting farther and farther from every day.
Ah, gun control. I'm with Twi here. Ideally, there would be no need for guns (outside of hunting). But as that's sadly not the case, I believe guns, as long as they're used responsibly, should be allowed. Also, see the 2nd Amendment.
Basically: don't ban guns or restrict them to the point of uselessness, just teach people to be responsible. It's perfectly logical, I think, to have regulations. Just don't take it to an extreme.