I know the dog thing seems to be the way to go, But what if the dog actually got them, and they got away, told there mates about this house the went to jack and the dog bit them, and then all of there mates came over and killed your dog.

I suggest electric fence running off the mains.
We have that system set up at my property to keep my stallion from my mares. It gives you the biggest kick in your life with out actually killing you ( I know, i got zapped couple of times from it )

1 Zap dropped me like a sack of potatoes, and left a perfect red line across my hip and i was dazed from it, I actually fell asleep straight after it happened for 45mins.
I say do that! You can get everything you need from the farm shop, or any stock feed.

But seriously, i think you should move... Sounds like your a prisoner in your own property..

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Hey... Its that kid with a head!