24 miles in a day is a long day but feasible. I've done 18 miles walking, starting mid-morning and ending early afternoon. Running one way would shorten the time needed (though would also cause faster exhaustion, I presume).
For someone who runs distance seriously, 24 miles is pretty normal. This is not to say that the OP is on the level -- I'm also skeptical of the martial arts claims, among others. If the kid has a real problem with video games (and with the family life he sketches out, anybody would have some problems), sure, OK. But the whole thing reeks of fabulist nonsense.
Nah, sometimes you just don't want to run anymore. I've definitely done 10k runs, and just stop and look for a bus home. It's not even that you're too tired to run (though that plays a role). Some people can just keep running as long as they keep in the flow. When you lose it, running quickly becomes boring.
The other sounds less likely...