First of all, this was a great episode. "Disaster" episodes are pretty few and far between and well done ones are even rarer.
That said, you wonder if Mark ever became traumatized because of his upbringing? He sees all these horrors that his father endures, shot, dragged, beaten, exposed to lethal diseases and more. He's put into others care on multiple occasions, "in case" Lucas is killed. His mother has died and his father seems to be a major risktaker.
Sure he's a good kid with a level head, but at the same time, from a time when no one was an emo brat, but still all those repeated exposures to exceptionally high stress can't be good for him. I'm not talking the rough and wild west, no one in that time would've endured a tenth of what Mark has, let alone so repeatedly for so long. Years of exposure to stress like that would've done a number on him.
"Dessert" makes me chuckle in the episode description.