Barrels cannot be printed and last more than one shot, no. However, it isn't that difficult to rifle a hydraulic tube using Electro-Chemical Machining using printed parts for the mandrill. There still needs to be a lot of other metal parts like screws and springs, so they are detectable with metal detectors, but you can make a reliable firearm without any actual firearm parts. Look at the FGC-9 or Partisan-9 as examples.

Dammit, made the same mistake as him, not 2012

The S8 was released in 2017, not 2017

A DOD level wipe is 3-7 (Depends of classification) random-write passes on the hard drive. I have seen older servers take 2-3 days. As long as he ran them over a degausser (takes 30 Seconds) his disposal method is approved. (BTW I am a DOD contractor and just had to dispose of 652 hard drives from old systems, the degausser was a god-send)