The all or nothing response was correct, with mold you can't do a hit or miss job, or it will come back. It can be treated with a biocide and application of a biocidal encapsulant. As for the ventilation, you are probably correct as far as a high level of moisture pssibly being the cause. However, for proper ventilation, you need to find the total volume ( cubic feet ) of the area to be ventilated and size the fan for at least tthat amount. Then, you have to determine tthe amount of free space ( vent area ) to make sure you can flow that amount of air through the space.