I received the message you sent. I can understand your concern given the nature of the problem. And with some expierence in residential construction I can provide my opinion on the subject and maybe provide answers your questions.
First - There is really no way of knowing IF an existing home built during the housing boom in the 3 areas you were questioning were constructed with that particular material without removing panels to see IF they were stamped or labeled with the manufacturers info. Not all panels are labeled and not all foreign manufacturers follow US manufacturing regulations and guidelines. Quality wallboard is made primarily with gypsum, whereas a lower (or cheaper) grade has flyash included, which is a byproduct of coal burning (thus the sulfer compound) and primarily used as an aditive in concrete.
Second - Another option in determining if it was used is to contact the builder of the home(s) during that time period. Unfortunately many builders went out of business since that time and that info may not be available, or given due to possible liability issues.
Third - The use of the material (from info available) appears to be predominant in the southeast region (gulf coast states) where the climate is moist, humid and hot, and used as a result of a shortage of domestic materials. The 3 areas you were questioning are in an area which is predominantly dry and hot. Now that's not to say that the possiblilty does not exist or should not be a concern.
Personally - I would be more concerned with other possible problems such as: IF the property was flooded, mold would most likely develop before any emmisions of toxic sulfer gases from the material. IF the property was built during the boom, was the pad compacted sufficently before the foundation was poured to avoid settlement and cracking of the foundation. And when the foundation was poured, was it allowed to fully cure before construction of the structure to avoid cracking from the structure's weight over time (which has happend in the Anthem area to some). And is the property located in a known area for ground fissures which are caused by depletion of ground water from pumping (Queen Creek/San Tan area) and can open up after heavy rains and cause structural/property damage. And the usual concerns such as radon gas and termites or other infestations such as ants, roaches and scorpions.
All of which can affect the health, safety, soundness and the market value of a property, in addition to the amount of foreclosures, inventory/supply, location, amenities, environmental and economical factors of the market area.