This man was asked dozens and dozens of questions. Here's a few:
"Have you not asked her why [she moved out]?"
"Your timeline is very confused. You say you have 50/50 with her with the youngest but she just moved out. Which is it?"
"How is her relationship with your younger son - is he safe and loved in her care?"
"How was she harsh to your eldest? Did you chat about alternative approaches for discipline? Could she explain what her reasons were for chosing that approach?"
"What was the nature and frequency of your son's "trouble"?
What was your son's response to being grounded and having his phone taken (and by that, do you mean you've left your 15-year-old with no phone at all, or just for a period of time)?
In what way specifically do you think your wife was being "very harsh on him"?
What specifically did you do in response to your feeling she was being too harsh?
What else is going on in your marriage?"
"How does/did your eldest treat her? Did he have a tendency to do what you asked him to but not what she did?"
But there are no answers, because he does NOT want to answer those questions. He doesn't want our insights. No, what he really wants is for us to support his narrative that she's "harsh" and "depressed", that she's all of a sudden gone inexplicably mental, and that it's got absolutely nothing to do with him.
It seems obvious that the wife had to carry the whole mental load of the family, the eldest kid has behaved horribly, and OP has undermined her. That is why he is NOT answering our many direct questions on what really went on - because he doesn't want us to figure out the real story.