It would be easy enough to supply all the evidence on hand to FBI, but given this guy's level of persistence, I suspect most of the IP data is spoofed. Who knows, maybe Jim Rob already has cooperated with FBI to catch/trace this stuff as it comes in. I'm out of that loop to be sure, but Jim's a smart guy, so it's possible.
Anonymous and high-anonymous proxies can be denied.
I'm afraid you're probably right -- though with persistance, there may be a means to still track him...