I would use a non-emotional, matter-of-fact approach.Rather use a carrot than a stick? 

I'm not going to get emotional with this, however, even though we are excited about our first purchase.I'm not sure how to calculate the payback.

She came back with a first emotionally plea and then of course the blackmail with accusing us of letting them live in a house with mold and her children getting sick from it and she having to take them to the hospital.We have always responded to all maintenance complaints in a timely manner and also addressed the rather small mold issue (water leaking through the side of the back door, replaced the whole door).Now, where do we go from here?

No place for emotions, especially compassion.

If you search Emotional Support Animals Certificate there are a multitude of sites offering certificates.  

Your emotional issues are not here problem unless she wishes to address them.You will need to decide to live there or bite the bullet and move.

So if you sell it without the appropriate disclosures, and 6 months later the buyers find out by talking to the neighbors, and find that it was well-documented and you obviously knew about it (you even posted about it in online forums), do you think they might be angry enough to sue you for damages (to include their perceived reduction in value, physical/emotional distress, moving costs, loss of income, etc)?

yet, due to HUMAN factors, emotional factors, like the rather sudden shift of people moving back to urban areas after decades of nearly everyone, especially retirees, wanting to move OUT of urban centers for the suburbs.

My wife and I sacrificed a lot of energy, money, emotions, almost our marriage, ETC a little more than 3 years ago to get my son and his live in on the road to recovery from meth.

If they are emotional then talking about the deceased when you go to the home is, in my opinion, a bad idea.