The Second Amendment does NOT give you the right to bear arms, God does. The 2A prevents the government from infringing on that right.
If anyone argues with you about that, tell them to read the constitution again and stop arguing in bad faith.
You are correct.
The underlying natural right is properly defined as a "right of the innocent to defense against the unjust aggressor", as a positive extension of the right to life, liberty, property: this all starts with having a proper anthropology.
This is one of very few natural rights that had a corresponding duty on others: you'll note it doesn't say "self-defense" (although that too is implied).
Other rights that have a corresponding duty on others are things like: the natural right of the individual to public truth, the natural right of assistance for the unable (i.e. to food and water, it's why Aquinas affirmed that someone stealing bread from someone who is not in need to feed someone who is in immediate need is not an evil (which evil being properly defined as "the deprivation of a due good").
There are various levels of formal and material duty: formal duty is that which requires (positive) assent to happen, and material duty is that which requires (negative) permission or marginal utility to happen. (So, votes, judgements, legislation, and private agreements are formal things.)
This duty is attenuated, but not nullified, by 'moral distance' (proximal versus remote). The reason for this is that we are finite: moral proximality has to do with how many independent moral agents are involved in the chain of enablement. So, a vote on legislation is a formal approval that is morally proximal. Buying things from China is materially permissive and morally remote: many people are between you and the bad things going on in China, most of which are not defective.
Further, we can learn a few other things from the proper definition: there is 'just aggression' (which is directly contrary to the PNC, which is why anyone could
lean libertarian, but why nobody should actually be a libertarian: PNC and being entirely laissez fair' is, strictly, a defect of a due good). The 'aggressor' could be an individual, but it also could be a demos - the will of the majority can be itself unjust, and it is right to defend the innocent from the will of the majority (for Aristotle, this is one of the fundamental differences between a 'polity' (good) and a 'democracy' (bad))
Finally, since (almost) none are completely innocent, the 'level' of innocence required is in that context of the aggression: a police officer beating an unresisting drug-dealer is morally unjust, even if the drug-dealer deserves a beating. This is the essence of the 'presumption of innocence': the State (which derives from the people, says Aquinas) is attempting to restore justice (to a greater degree) by using aggression, and (ought) limits itself to only good means with no defects.
Finally, finally: in the final tally, the truth of innocence must take precedence over the good of justice within the imperfect and finite framework we find ourselves operating in.