The next time he climbes over the fence, shoot the little fucker.
Fortify or move. Whichever is easier.
Next time you see the kid climbing over your fence, call the cops. Parents are obviously not watching the kid and that constitutes neglect. Remember, if you own the property and the kid gets hurt, you are responsible if you do not attempt to get him off the property.
You can also call your town/city/village hall and complain about the messy yard. Lots of municipalities will force people to clean up.....maybe yours will!! As for the kid, call the cops like someone said, or better, call your local social services and tell them the kid runs free without supervision AND the house is filthy!!
now's the time to polish up on your bulldozer driving skills, and what better place to practice? :)