I agree the original intent was focused on militias, not on individual gun ownership. and I agree it was for the purposes that you list. Still the constitution did not give the federal gov authority to regulate the militias, it only states that they be "well regulated" w/o stating who is doing the regulating.

At that time, as with today, there is a fear of the power of the federal gov. So the founding fathers would not have liked the idea that the federal gov was regulating those militias.

But we live in a new world today. Back then, the weapons that individuals have are comparable in power to the weapons the military has. Today this is not true. Basically if the military decided to oppress the population, there would not be a damn thing our little pea-shooters at home could do about that.

So the main reasons for the 2nd amendment are pretty changed now.