I'm convinced that we have an almost entirely different perspective on the COTUS than did the founders.
Consider that until at least the Civil War, most people identified themselves primarily as citizens of their STATE, not The United States. They were "Virginians" not "Americans".
The founders likewise identified themselves by state rather than nation and intended to form a national government that would protect the states as a whole, "oversee" the relationship between the states and maintain relations with foreign powers.
The states had (or would create) their own constitutions. The COTUS did not and was never meant to be applied to the states. Consider that a number of states actually had official states religions, which were not challenged by the founders as in some sort of modern "incorporation" idea. Official state religions were not (and are not) violations of the COTUS because the COTUS does not apply to the states.
Consider also that many states have their own "2A" (as well as duplicates of virtually every other right) in their own constitutions. Why would this be if the COTUS applied to the states? It doesn't make sense.
At the time of the founding, the people were in control of their states. The state governments were small and more trusted, the founders didn't fear the states. They feared the overseer. The people took care of the states, and took care to write their constitutions to address whatever fears they likewise had about the powers thereof.
The COTUS was written to protect the STATES (the "people" as a whole) from the NATIONAL government.
The prefatory clause to the 2A, I believe, is tied to the reason why the NATIONAL government would want to disarm the people. The national government really wouldn't have any other reason to disarm the people, except to fear their militias.
Therefore, the prefatory clause isn't the reason why the people HAVE the right, it is the reason why the government might want to REMOVE that right.
The essential meaning is:
Since having a well regulated militia protects the people from the government, the right of the people to keep and bear arms shall not be infringed, lest they lose the ability to protect themselves.
I believe that other uses of those arms, such as individual self-protection, are completely unaddressed and rightly so. They are issues of basic choices of daily life. They aren't mentioned, I believe, because the founders never considered that we would so lose control of our government, that we would so lose sight of it's purpose and allow it so much power, that it would even be conceivable that the NATIONAL level government would ever be concerned with such trivial, daily life choices of individual citizens.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.