I would imagine the best actions would be to immediately fire the management company, pass the keys onto a new one, sue the old one in small claims court for the listed damages.

One block may be legal, the next block may not be.

Often times when a builder/buyer moves too fast, or is too busy and overlooks a key piece of due diligence, the unethical ones will try the "scorched earth" method and blame everyone but themselves, even when they know it was their own mistake, and they'll see if they can scare you, the seller, the title company et al into paying damages/fixing their problem. 

Sounds like an unreasonable seller and the most likely reason for them not wanting an offer with a financing contingency is the property is in too rough shape to get financing on it (structural damage, fire damage, etc.) or won’t appraise anywhere near asking price.   

What steps would you recommend to minimize damages and resolve this issue efficiently?

IF you don't know the number or the caller, don't answer and block. 

So I am not completely sure but maybe it is because it was blocked for so long.

Would very much appreciate opinions on whether Canton, Ohio is a good area for buy and hold or flipping, specifically within a few blocks of intersection of routes 43 and 172.  

Our house is in the R2 zone (4 blocks off main) and the process to transfer the permit back in March was a breeze.

Especially if seller just received a windfall from the sale it is definitely worth suing for damages.