That's not actually correct, it says "arms", not "some arms". If you take guidance from the "militia" part (possibly dubious, as it's generally interpreted as a preamble), a militia, in a current defensive war, would require anti-tank and anti-aircraft rockets and missiles, at the very least. The problem with that is, in Heller, the militia is not really part of the test anymore. You might be able to argue against suitcase nukes, and they don't really have a defensive or targeted offensive purpose, and are only really useful for terrorism.

And yet, you can't buy anti-tank or anti-aircraft weapons.

You actually can, if you can afford the paperwork and storage requirements.

It's quite involved and expensive ($200 tax per round on anti-tank rounds just to start with), but it's not impossible. Just prohibitive in cost.

The clear intention of the second amendment is that the citizens have the right to have and carry around anything that would be needed to wage war at the highest level, in order to defend themselves from anyone including the government. Just as the founding fathers had very recently finished doing.

You are clearly correct. All constitutional scholars seem to agree on this. The founding fathers were very concerned about the possibility of future tyranny from government they were crafting. Ensuring that the citizens had guns, and limiting the power of the government were both ways to prevent such tyranny. It's a shame that more people do not understand the mindset of the founding fathers. (Not to imply that they all had a common view on this. There was much disagreement and negotiation.)

I don't think that's the clear intention at all.

If that were so clear, we wouldn't have all of the litigation and laws around the 2A as we do.

It's only not clear to people who wish the second amendment said something else.