I apologize for this back and forth, but the advice above is so bad I feel I need to comment. First, nothing you've said indicates extortion. Extortion is the act of obtaining money or other property from a person by threats or force. I did some research for you, and Tennessee has cyberstalking laws, meaning his threats via email could constitute a crime. You could go to the police. I still advise, for your protection, seeking a no contact order. A police investigation will take time, and in the interim, this person could be a threat to you.
Why you would start a civil suit, let alone in CA, I have no idea. That will take many years to resolve, and might result in a small monetary recovery. That doesn't seem to be your concern at all. Moreover, by continuing to threaten you via email, Tenn would have jurisdiction over him. Unless you wish to make dozens of trips to CA, which you'll pay for, and hire an attorney in CA, I see no logical reason to commence a civil suit.
A Tenn court will have jurisdiction to impose a no contact order. Moreover, Tenn will have jurisdiction to prosecute the person; however, to do so, the state attorney must be willing to jump through hoops to have him extradited to Tenn. It's a lot of work and effort, and this isn't a major case for them. They may not be willing to engage in that endeavor.
A court would, however, impose a no contact order.
Good luck. I hope things work out.