I had another thought, and I'm glad I got back on the PC after reading all this!

If the cookies and neighborly chat don't work, maybe contact a behaviourist. Then, if things escalate and the police get involved, being able to show you got someone official involved and he / she estimates it will take "this long" to fix, may help. The place where you adopted may be able to recommend someone.

Once upon a time, a new young mother had a baby with colic. The baby cried and screamed and basically drove everyone crazy around her. The neighbors complained to the police, worried that maybe the baby was being hurt. Fortunately, the mom and dad had already taken the baby in to the doctor, had the diagnosis of colic, and were in the process of switching foods. They could say it would take XXX amount of time - just a few days. The police DID contact the pediatrician, just to make sure this was all true.

I was that baby.

Good luck!
Sandra