My deck is in the same condition. I just hired a crew that's going to shore it up, move the stairs, and replace all the railings. They're going to start work on 4/6. A company located in Buford. Shoot me a PM if you're interested in their info.
You have more self-control than I would've had. I would've beat his ass then called the law. Since you had trail cam pics of him trespassing before you would have been fine.
Nice job not letting that frame go to waste. Looks like a great project and you'll have a nice trailer when you're done. The boys will enjoy helping I'm sure.