Not much.
That your current tenants were "interested" in buying means nothing. I had rentals for 20 years and had numerous tenants "interested" in buying but when the time came for them to put their money where their mouths were, they didn't. So you've got nothing there.
If your current tenants are on a lease of some specific duration and they break the lease because of the harassment you might be able to recover any actual monetary losses from the neighbor who drove them out. But then you would have to produce evidence (not just sayso) that the tenants were driven out by the neighbors. I doubt if your tenants will come back to testify in court for you once they move out.
Frankly, what I see you experiencing is the usual consequences of being a landlord (I had worse) and if you don't like taking those lumps, sell the property and don't look back. That's what I did.