I second what Noah said. I've struggled a lot with my mental health back in the days and you change a lot throughout the years.
He's 12, I'm not saying all will be fine when he turns 13, 14 or even 20 but there's no way you should feel guilty about getting your account back.
I see some disgusting reactions here though so I'd thought I'd post my opinion.
He just needs someone to vent to. Sure it's good to keep your mind off things whilst playing runescape on a maxed account but that's not going to solve it.
There's also no way you'llbe able to make this clear to him. He's 12 and not yet capable to think further in life.
I said some massive shit things when I was 13-14 and was mentally very unstable and life experiences have made my view on life change hella a lot , not the fact whether I had the ability to play on a maxed account or not.
Sorry for being personal