This is not correct. The relative rates of clocks depend on the difference in gravitational potential between the clocks, not on the field strength. Although those things frequently change in the same direction, they don't always and they are very different things. An obvious case is if one were to drill a hole to the center of the Earth - clocks held lower in the hole would tick slow compared to clocks held higher in the tunnel all the way to the center, but the acceleration due to gravity decreases to zero at the center of the Earth. So the place you'd feel zero weight would be where you also measure the largest time dilation effect.
Furthermore, your experiment is misconceived. To make comparable measurements of time you need clocks that operate the same way under all conditions of interest. For example, a steel clock would operate strangely in a strong magnetic field, but that's not evidence of time acting funny in a magnetic field - it's just a bad experiment. As you yourself note, pendulum clocks don't tick at the same rate in different gravitational field strengths. So time measurements taken with identical pendulum clocks in different field strengths aren't comparable, just the same as the steel clock's measurements in a magnetic field would not compare to the measurements it makes normally.
Edit: you can, of course, calibrate pendulum clocks to some agreed standard at arbitrary local ##g## value, and you will (in principle) be able to detect time dilation between them, just as you would with atomic clocks. In practice I do not think a pendulum clock can be made precise enough to do this, but it's possible in principle.