Cimex is harmless micro silica that sucks up moisture (it is used to keep electronics and beef jerky from getting damp and moldy). 

@Nam TrangThe inspectorI don’t think there is a negative to removing it.If you are doing a long term rental, it will drop leaves on gutters and roof retaining moisture, causing mildew, and clogs, eventually riots will become and issue, although with a crawl space foundation, that’s probably easier to live with/work with.If you are doing a flip, it looks awful and future owner will be worried about the above.

Gently mention and apologize the train and say that it is not normal, then highlight the specific nice things they said about your place.It's kinda silly that Airbnb asks guests for an overall rating first, then gets sub category ratings that have no impact on the overall rating.

Their website says that infrared scanning is "using the most technologically advanced tools available allows us to detect moisture that is invisible to the human eye, and with these we are also able to locate areas throughout a home or structure that have overheating or malfunctioning electrical components. this work brings a critical difference to a home inspection". 

I would also keep all interior doors open so you can draw the most moisture out as possible.

The issues with expansion and moisture issues cause tons of problems according to him

Perhaps your tenants can get their animals to piss where the soil is dry, so it will be more moist such that it will absorb moisture when S/he hoses down the area.

I don't like hardwood flooring in rentals because: 1) They are expensive to buy and expensive to install; 2) They require maintenance; 3) Re-finishing floors is also expensive and extensive; 4) They are not water proof/temperature proof and will buckle/warp if there is excess moisture from a leak etc. ; 5) Pets may leave gauges in the flooring from nails; 6) Compared to LVP they do not add any more $ in value LVP is nice because: 1) It's less expensive and easy to install; 2) Is water proof and scratch proof; 3) The thicker wear layered planks i.e. 12mil or higher will last longer than hardwoods unscathed; 4) its pet proof; 5) In the off chance that many years down the line there is wear on the floor, you can replace them still for cheaper than you can refinish hardwood flooring, and its a new floor again. 

The cardboard will kill everything under it and prevent weeds from growing and the mulch will help keep the moisture in the soil.My tenants are responsible for maintaining the yard and most do a good job. 

When the source of water intrusion is known, and the spread of moisture is measurable and its known that the biological growth is spreading from the source across an affected area - what is the point of testing what is already known?