Here is a play. Spacing is controlled by the two sliders in the blue group while “resolution” is determined by the PFrames ‘N’ input (top left).
As @rahul1 mentioned, your lower curve is not continuous, making lofting impossible and isocurves irrelevant (why is that word in the title?). It’s also not directly below the upper curve in some places. Both these issues add complications.
P.S. This is the same code but using @akche001’s more carefully constructed curves instead of yours.
P.P.S. The blue group sliders can be adjusted so that vertical lines are more closely spaced when top and bottom curves are near each other, just the opposite of the spec.