Another option is to reach out to the
Cryptios team. They have access to some IP data for users and their accounts when they log in, to help with account recoveries or lock accounts that seem to be acting suspicious. Not sure if they will respond but that's the route I would go to clear my name in this situation.
I dont think he needs to prove his innocence. The OP needs to prove guilt. He can report the PMs to a moderator who can authenticate the PMs.