Well..this is a jam. If you change your account/access and all and do what you can to resist his contact attempts, You then basically have two options - you can 1 - call his bluff...tell him to piss off and leave you alone, or you will contact the police - cause he is an adult who manipulated a underage child into sending him CP - so go ahead. Right now he is only in possession of CP - so go and send the pics to my friends - then you will be held for distribution of CP as well...as they will report the crime for sure. So it is a lose lose situation for him.

OR 2 - you break off contact and simply contact the police and forget about calling his bluff and let them take it from there. Let him get his door kicked in at 4am by Mossad..

You made this mess--so if you want it to go away you need to own what you did, and learn from this and take action against the guy one way or another.