yet he has the right to screw him up because of it
No he doesn't. I doubt anything would be done about it. But I know how it feels. I've had this happen to me before. I didn't scam, but I've lost all of my things.
I don't I was honestly just planning to take the email and the steam account and let him keep the $10 because I'm a nice guy
You should take your steam back and go. Can you not change the email for the steam account to prevent him from recovering it? If not, then take the email and don't touch his things. Be nice c: