I think taping someone on the phone without their knowledge is illegal and inadmissible in a court, unless you have a warrant to do so. So it may not do you any good other than letting the police know your not making stuff up. And from what I can tell your not the type they would discount easily.

Sounds to me like you got things covered though, I would just suggest you let the land owner know what is going on but you probably already know that as well.

Good luck, let us know if anything comes of it. While there are a good share of nut jobs around most are just talk. Never hurts to be prepared though.

Paul