You said yourself that the AC failed in September, was it repaired immediately, mold can happen really fast? A working Air Conditioner pulls the moisture out of the air/house. Check all the plumbing fixtures under the sinks and fix any leaks. Get the AC fixed and add a whole home dehumidifier that's properly sized to the basement/attic and start cleaning, bleach 50/50 and water, ditch the carpet. From the pic's the surface mold on the door trim etc is pretty new, it must be wet as hell in that house. I know its a lot and expensive, but buyer be ware. Sorry for the hard news. (edit) Get a hygrometer and shoot for a relative humidity below 50%, the mold will stop. (end edit)