Again, answering your second question first, the simpleanswer is NO, Congress is NOT acting in the original understanding. I think there are some complexities there, but essentially, there are few disagreements there.
With regard to your comparison between drugs and guns — again, are you freaking kidding?! The 2nd Amendment guarantees the right to keep and bear arms. It is essential to liberty. There IS no right to keep and use recreational drugs! No matter WHAT penumbra you look under in the Constitution! I show no contempt (I find that mildly insulting) for the Constitution in saying that it does not protect the “right” of individual criminals or groups of enemies both foreign and domestic to destroy the nation and the several states both morally, physically and economically. That’s patently absurd.
Reread what I wrote. I did not compare the RKBA to a right to keep and use drugs. I compared support for Amendment II to support for Amendment X. Support for Amendment X means the states should have the choice regarding intrastate drug policies, not that they must legalize.
If fedgov passed a law requiring states to legalize marijuana, then that would be just as much a violation of Amendment X as are the current laws which impose national prohibition. Attaching conditions to one's support for either of the amendments is a display of contempt, IMO.