Be sure to get mold testing done after remediation and removal of drywall areas so you have a record of clean air following the remediation if anyone were to ask, but you shouldn't need to provide this information unless requested.

Did you show the seller in writing from a GC that it would take $90K in repairs or did you just pull that number out of the air to get a better deal?

If it's as bad as you say, you may have to replace the a/c unit and possibly the air ducts, just something to think about.  

I do see you may want to do central air & heat...

The evaporator coil must be clean of any obstacle, this way the air will flow.

Once the house was lightly staged with furniture, we put air fresheners throughout the house and listed it on the market.

Also, what clauses outside "and/or assigns" should I make sure are absolutely in my purchase agreement & is there a way to make it air tight legally without paying an expensive fee for legal review?

Also it's hard to negotiate from a position of weakness and it sounds like your case is less than air tight.

If you are soon taking the Florida real estate exam, check out my You Tube channel.

All we did to the house was clean and paint, it already had a 4 or 5 year old gas furnace and central air.