I'm sorry, but travelers to a foreign country need to be at least cognizant of local customs (read the section in a travel book before going), and if they break the rules, expect to face consequences.
My take is NK will make sure he kept in a good conditions, possibly exposed to some made-up farmers views playing "hard labor prisoners" to make sure he will eventually report that no atrocities are taking place and with eventual return already planned for him on a horizon.
Not to say that actual NK citizen's lifetime for equal "offense" will likely be drastically shorter.
Letting US citizen to die in NK is not going to have a healthy consequences for "the leader" and he realizes this pretty well.
What North Korea is going to do to this kid is going to be inhuman and totally disproportionate to what he did, which was, at worst, fairly stupid.