It turns out the density calculation was always correct.  I read back through the email where David and I carefully and independently calculated the number of molecules to get from 1M in Å as well as the expected spacing between molecules, etc. and it should be densityInMol*0.0006022*VolInAngstomsCubed.  We will, however need to change the surface density calculation to match the same exercises David and I did in the email October 16, 2013 “defining concentrations in cellpack”