Also he's 16. I'd definitely be less willing to push back (especially on something like this) at his age
Of course not. You don’t push back on something like that. You hire a lawyer and let them do the pushing for you. If you contact the right NGO, they might even give you one for free.
There’s no way I’d sign any agreement with a company like Microsoft regarding an issue like that without a lawyer. I’d rather not disclose at all if those were the only options.
At that age in the mid 2000s, I would be foaming at the mouth to tell a FANG company to eat dirt over something like a disclosure + unpaid bounty. But if he got the money and didn't negotiate... You live and you learn.