he could be testing his own mettle. “how much pain can I endure”, boredom (back of the car, possibly no electronics or something), emotional numbness with pain being the only thing that feels real…
I think as long as you both support him in spite of the divorce – your love for him
framed in a way that doesn’t Have THE DIVORCE woven all through it, you’ll be ok.
“Your mother should have…” is a phrase I would ban for example.
what’s his hobbies? what makes him different from his brothers?