It’s very well established colonial Americans could own the most high end and powerful weapons of the period for their personal use and continued to do so until around the Civil War, this being large cannons. It is also well established the founding fathers understood technology advances and the second amendment should cover any future weapons of war. See private ownership of cannons, privateering, the St. Albans Artillery Regiment, and the Kalthoff repeater for more details.

Your misreading of the second amendment is the main reason you have this viewpoint. When most people think of the second amendment they think of its purposes for hunting, recreational shooting, or self defence against other individuals. However, the purpose of the second amendment is to keep the citizenry armed against the government itself lest we fall under a tyrannical government again. The militia in this case is standard citizens using their own arms against the government in ad hawl units. The founding fathers just fought and won a war against such a government mostly because of their ability to acquire such weapons, and the first thing Britain did when they suspected rebellion was attempt to ban weapons.

In any case, your last point is true. It is just a word in an amendment to the highest document in the land. In which case it takes precedent to all other laws. If you wish to control arms, you need to have an amendment to do it, and until then they shall not be infringed.