Seller had previously wanted more cash for purchase, I countered that we would walk - it turned out to be an empty request as they accepted my "No."

Go to your county courthouse and request civil court records / eviction filings (every county is going to be different, some will be easier to work with than others) 

Any objection to that request means you're dealing with a wholesaler. 

I can't imagine how many horrible leads come in since the advent of Trulia, Zillow, etc. and the one-click "Request Information" buttons.  

A quick example, a tenant threatened to sue for health issues relating to black mold (home has never had any water issues or reason to believe there is mold), because I denied their request for a new washer machine (old one works perfectly fine).

Has he not responded to that request?

Also I will definitely be requesting a lower price considering that the boiler is shot and the windows also need replacing.

Send a letter to PO box and in red ink  outside envelope mark " ATTN Post Master;  Forwarding Address Requested".

He twice sent texts telling me he would ‘respond’ to my request when he was free; however, as I previously mentioned, I told him that his response was not needed.

Never ever ever ever again. ever.When they want something from you, they demand immediate action (Ex: Calling at 10pm to tell me my tenants had put a small yard gnome in the flower bed outside their door, demanding its immediate removal.)But when i requested that the dry rotted outer door jambs be replaced (per by-laws stating they are responsible for "from the studs, out") It took nearly 6 months of emails, phone calls, threatening legal action, and finally petitioning to have the president of the HOA removed.