Paris rocked Janeway's world. Like father, like son. Nepotism was a factor from day one. Why do you think he got real pips instead of the Maquis tabs.
Would he have had the proper codes to enable him to activate the self-destruct sequence? I thought only the Captain and First Officer and other senior staff had those (ie. CMO, Chief Engineer).
I dunno. On every other ship in Trek you had to have several officers turn on the self-destruct. Janeway instead flipped it like an on/off switch.