But dont harass them in the interim.

Of course you can assign the debt to a debt collection agency and get round two of moral victories with the harassment they create, but that too is hollow.

I recently received a letter from my tenant wishing to end their lease early due to continued harassment from their neighbor.

They have borderline harassed contractors we have sent to the house (pool service, landscaper, etc.) and we have caught them in several lies (verified). 

I feel like this is a form of harassment since we have never been late or said where we're going to be late.

(B) If the landlord makes an entry in violation of division (A)(8) of this section, makes a lawful entry in an unreasonable manner, or makes repeated demands for entry otherwise lawful that have the effect of harassing the tenant, the tenant may recover actual damages resulting from the entry or demands, obtain injunctive relief to prevent the recurrence of the conduct, and obtain a judgment for reasonable attorney's fees, or may terminate the rental agreement.

Tells me that I'm harassing them when I suggest them ways to save money by not using overnight option and insuring rent check envelope.

I just was simply tired of getting harassed every waking moment of the day for showings.

I'm curious about the following:Can creditors keep contacting/harassing the Rep about debts owed by the Estate?

At the minimum, you get a chance to harass them for being a terrible human being even if you don't get anything back.