Because concrete is really porous it's very difficult to get everything out of it once it's in - usually you're only breaking down things right at the surface and they tend to bleed back through capillary action (moisture moving through the concrete).

I use over the range microwaves in all my rentals; it's just one less appliance renters need to bring and gains huge real estate in small kitchens, and the microwaves are almost the same cost as the hoods any more.As for the countertops the spots that always get ruined are the areas exposed to moisture; the clear poly repels the moisture and binds the sawdust together in the particleboard.

Typically the "bug killers" would've mentioned German Beatles (VW's lol) to the homeowners.A couple things you may want to look into are too many type NM (slang is Romex) cables in 1 penetration and not supported.

Have an expert look at it.I understand that you want to avoid setting untreated wood directly on concrete because the concrete attracts moisture that rots the wood. 

Moisture in ceiling; subfloor damage.Moisture in ceiling; staining and previous repairs.Moisture in baseboard and floor.Moisture in ceiling; staining.Moisture in ceiling.Roof replacement; address moisture and leaks.Exterior inspection; identify and fix moisture sources.Fix moisture damage.Electrical system overhaul; ensure safety and compliance.Temporary housing costs for tenants during repairs.

Crawlspaces/subfloors are particularly bad about humidity and moisture issues. 

If in a high humidity area out a moisture absorber in the batter compartment and put it on your cleaners punch list to change out twice a monthhttps://a.co/d/hjR2Spd

This definitely seems high from my perspective, although it depends partially on how many valleys and roof penetrations there are.

Mold needs two things to grow: moisture and food.

I have a feeling there’s moisture getting in between the walls.