Which govt level is actually keeper of the CoO?

A lot of it depends on what your income level is at and how much your debt is, etc.

I'm not sure what your current experience level is, but through volunteering with this organization I was able to get hands on experience at various stages of construction of new homes.

With the roof gone and if the first level is finished then you need to protect this space from weather/rain or you may be gutting this too.  

Yeah.. until the AOS is signed and the earnest deposit is received, there is nothing legally binding them to a verbal conversation or agreement.If they are willing to dump you for the new guy, you may be lucky that you got out of that deal.Lick your wounds, go on to the next one.

While the strategy is ok on a basic level, I want to advise you not show up to the table with the " beat up" attitude.

They would usually make sense of it on the assignment to AOS gap, but real cash buyers don't care either way.

If you want to keep track of the economic trends that impact local RE values, there's no better nor more pessimistic news outlet than Seattle Bubble, which is constantly scanning for signs of price devaluation and parses the factors down to the DNA level. I

But at the national level, I don't think we'll see the bottom drop out in the housing market at such a massive scale any time soon.

It may be that the water activity level is just too high for mesophillic molds to be growing (those are the most commonly encountered in water damaged indoor environments like aspergillus and penicillium-types).