I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
You can block the user and ask people who know you to do the same. You can also report the user. Facecbook should be able to delete their account. What the Facebook rep told you doesn't make sense. If they're saying things that amount to threats, or if this is an ongoing pattern of harassment, you can notify the International Crime Complaint Center and ask them to investigate. A lawyer can also help you subpoena whatever information Facebook has about the user, because Facebook usually won't tell you anything without a court order. If possible, it would help significantly to find a lawyer who practices in both Nevada and California (there are many in the Lake Tahoe/Reno areas, but I don't know where in the state you live). That's because a subpoena has to be issued by the California courts before Facebook is bound by it - that's where they're located.
Once you know who the person is and where they are, you can sue them for Defamation of Character. Defamation is any untrue statement of fact that tends to harm a person's reputation. The lawsuit has to be filed where they live, so the first step is to see if you can track them down. Another option is to ask a local attorney to send them a "cease and desist" letter, giving them a chance to delete the false posts and stop making more in order to avoid a lawsuit. If they believe you're serious, they may do it, and having a lawyer send the message tells them you're serious.
If you have any questions or concerns about my response, please reply WITHOUT RATING. It's important that you are 100% satisfied with my courtesy and professionalism. Otherwise, please rate my service positively so I am paid for the time I spend answering questions. If you are on a mobile device, you may need to scroll to the right. There is no charge for follow-up questions. Thank you.