As for the latter issue, Justice Gants makes what appears to be an unassailable point in footnote 8:
We also note that, even if a firearm were secured in the manner required by G.L. c. 140, § 131L (a ), a gun owner threatened in his or her home today would be able to fire the weapon in self-defense at least as quickly as would a gun owner in 1791, when the Second Amendment was adopted. At that time, laws were in effect requiring that gunpowder be stored separately from firearms, which meant that a law-abiding homeowner acting in self-defense would need time to load and fire a musket or flintlock pistol. See Heller, supra at 2849-2850 (Breyer, J., dissenting). A skilled soldier of that time using specially prepared cartridges required a minimum of fifteen to twenty seconds to load and fire a musket; a less skilled soldier could fire no more quickly than once per minute. Hicks, United States Military Shoulder Arms, 1795-1935, 1 Am. Military Hist. Found. 23, 30-31 (1937). A gun owner today could remove a firearm from a locked container or release a trigger lock more quickly than that.
If you're going to be an originalist, you'd better be prepared to deal with the consequences.*