That was the point of my 1st post. I absolutely think there needs to be some regulation involving firearms. However, POTUS writing an EO to do it would be the absolute worst way to try to implement it. Same applies here. Same applies to any limitation on any Constitutional Amendment.
Use the right process, pass a law that doesn't violate the applicable amendment or write a new amendment that supercedes the previous one (see 18th and 21st).
Entirely correct.
Modification requires either a law passed by Congress, subject to the interpretation by the Court on its Constitutional validity/legality, or an actual change in adding a new Amendment (e.g. Prohibition).