There is no smoking allowed inside any of my units, of anything - no e-cigs, vapor, cigarettes, cigars, pipes, bongs, joints, whatever.

Once the floor is clean, follow by an application of a vapor sealant product specifically for concrete (we sell this)  and an epoxy concrete floor coating. 

I was wearing a half-respirator (3M-7000 series) with NIOSH-approved organic vapor cartridges, as detailed in the MSDS of the product, but I could not achieve cross-ventilation, even with the door to the closet removed. 

This will provide a vapor barrier. 

The banking industry and wall street created "VAPOR PAPER" that had no intrinsic value.

Technically you should use a product such as stego mastic then cover it with stego wrap (a vapor barrier plastic sheeting that is basically rip proof) This must be from the top to the bottom and it will not be cheap.

What about the vapor barrier

Vapor barrier is ok as long as you realize that is what it is.

.- Asphalt Roofing Manufacturer's Association "strongly advises caution when considering the application of any type of field applied coating over installed asphalt shingles," due to possible shingle curling/warping and possible vapor barrier may cause premature failure of roof decking.- Some shingle manufacturer's specifically state that coating will void the warranty.  

You must ventilate otherwise you will condensate water vapors in this space.