If the hacker always use vpn then there might have low chance to caught him, but still it should be reported on FBI. Less is better than never. And if the person become careless for a while then there will be high chance to catch the hacker.
VPNs are not the be-all, end-all. The only difference is that now you're passing through some other network as a proxy but it's not as if the culprit can't be found out via other methods than IP detection.
The Facebook account is definitely going to be a dead end (at least analytically) - unless he's a total moron, there won't be information to be gleaned from investigating a fake account and the sign-up process is accessible enough to where you can probably create one in a few minutes.