I think it's time to file a police report about your trespasser. At least then if something happens to him, or you catch him harming your livestock(chickens qualify), you have headed off a lawsuit from the start. Next time you see him on your property, call law enforcement...tell them he has already been told to stay off your property...they will also warn him, and it will then be documented. Be sure you tell them about all of your experiences with this idiot.
I don't know where you are, but in California a person has to be warned that they are trespassing before they can be cited. I think the auto cams are a great idea...you may even want to consider fencing in your property.
Make it clear to the police when you do call them that your chickens are part of how you feed your family, and explain that only a human would be able to manipulate the lock. Your dogs would also be a great idea.
Good luck to you.