Headscratchers / The Winchesters

• Why did the Mars Neto case worsen John's PTSD and temper?
  • The case where Mars Neto was deliberately bringing John's PTSD and temper to the surface, and where John defeated Neto by beating him to a bloody pulp? Seems self-explanatory.
• Why did Tracy think shooting Mack would do anything other than pointlessly kill John?
  • Tracy's not exactly a paragon of clear-headedness in that scene. However, it would have eliminated the immediate threat Mack was posing to Mary's life, and it's possible she was hoping none of the rest of them were sympatico enough with Mack's mental state to be possessed like John was, giving them time to prepare for the next attack.
• How is the Impala able to traverse the multiverse? I get it's a duplicate conjured by Heaven, but I can't buy Jack allowing anyone to have that kind of power and not knowing about it.
  • Because Heaven things can do that, apparently.
• What are Dean and Bobby, exactly? They don't seem to be ghosts when visiting the mortal plane.
• Why don't the Monster Club ever use guns?
  • A lot of monsters are either immune to or only mildly inconvenienced by bullets and need to be killed in specific ways, or are better disabled by chopping or impaling them than by shooting them with lead. If anything, shooting around would be more dangerous to their fellow humans. Same reasons that the Scooby Gang in Buffy the Vampire Slayer don't use them.
  • Out-of-universe, since the core four are young adults, the show may not want to encourage gun use among young adults.