Now that I'm like a doggie with a bone on the van der Kolk stuff....
I've wondered why Ethan does bowling. His father mentions it in a text, yes? I can't make it fit with anything else. So, he's not at all into horses (which incidentally have been shown to be helpful with some "difficult" kids), rowing, karate, or polo, or lacrosse. So, what is the bowling thing? To me, bowling....I'm useless with the ball. But the one thing I do know about bowling alleys, they're noisy. And it's a particular kind of noisy. It's crashy and rhythmic. You hear the ball drop on the wood floor, then a kind of roll-y noise until it reaches the pins, then the sound of the pins being knocked out, then the machine setting them upright, then the ball rolling back to you and re-racking. 10 lanes or so of that.
Imagine if you were a kid with a lot of disorganized noise in your head (doesn't matter if you have a formal diagnosis of psychotic, just that you experience the universe this way), as Ethan does. But bowling gives you organized crashiness. And it would have meaning (namely the goal is to knock out pins). If I were that kind of kid, I could totally see myself wanting to be at the bowling alley. It would in a way organize the craziness in my brain.
This is just speculation on my part, but I do wonder about the bowling.