Have your lawyer advise them ALL that you will file suit and list the city as "correspondent" in any matter of damage or injury that ensues from that point on..
Get a restraining order..
Then load your gun, take it to the range, and practice, practice, practice..
You have the right to protect yourself and your family, and depending on the state, your property..
If the dog comes through the fence, KILL IT..
You pretty much described what I as in the process of doing when he moved. You should have been privy to all of the plans that I had hatched to legally dispense of the dog. And yes, I use the term "legally" pretty loosely. I really don't care, because when it comes to choosing between my family and a dog, the dog will always end up dead. And true, the jerk would have most likely tried it again, but "accidents" can come in pairs...