That's a tough situation. Not only the lack of recourse for the losses, but that future family members aren't more considerate of you.
The only other thing that comes to mind is to try electric fence. It won't do the dog any harm and he'll only get "bit" if he's trying to go thru the fence. Run it 3-4" from the ground if you can go that low and probably another couple of strands at 6-8" intervals above the first. Terriers are (generally) super prey driven and VERY smart, stubborn, focused, so this is a tough one. Good luck with the dog and the in-laws.
The only other thing that comes to mind is to try electric fence. It won't do the dog any harm and he'll only get "bit" if he's trying to go thru the fence. Run it 3-4" from the ground if you can go that low and probably another couple of strands at 6-8" intervals above the first. Terriers are (generally) super prey driven and VERY smart, stubborn, focused, so this is a tough one. Good luck with the dog and the in-laws.