RE:160 ft onshore vs 170 ft offshore Thickness by itself doesn't tell the whole story. In very rough terms you want to worry about hydrocarbon pore volume of the entire accumulation
gross rock volume (GRV) = thickness X area
Net pore volume = GVR X porosity (% of rock volume that has "holes in it) X net to gross (% of the total interval that is sand vs shale)
Hydrocarbon Pore Volume = net pore volume X HC saturation
Gross rock volume is your big lever, and in addition to the thickness you have to take into account area of the accumulation.
There's a whole second order question on producibility, which is an very length discussion in itself but your questions around saturations and the stacked nature/unknown water saturations in each means there's still a lot they're likely analyzing.