Neighbour harassment over boundaries
This is a tough one because we have boundary issues coming together with (what sounds like) harassment and abuse. Assuming you are in Ontario, our advice would be to hire a lawyer - one who specializes in boundary-related litigation. This is your clearest path to understanding the full scope of options available to you. The City will not help you as this is not a civil matter. The police will not help unless a criminal offence has been committed (and you can provide evidence of it). A land survey firm can help you identify the boundary "on the ground" but they cannot help you enforce your rights relative to that boundary.
So really, your options are three-fold:
1. Do nothing.
2. Hire a lawyer.
3. Sell and move.