Your ideas are honestly great and both of the solutions you presented (RSS->.gov site and public keys) feel like great solutions. I think the problem is that both of those require the general public to have some amount of technical knowledge which is, apparently, a big ask. The first would be a lot easier to present and avoid confusion but it'd still require people to know to go to that site.

For what it's worth though, I think the solution to that is people should have some real amount of education about the function and potential dangers of the internet before getting on it.