Oh good. Your .230" is thinner than my new springs were (.237"), so maybe yours are OK (or at least better).
Yeah, something pretty badly wrong with that calculator. Apparently, it is assuming that all of the leaf ends are connected rigidly together, so that the little short leaf (which in reality does very little) is the stiffest leaf. As a test, I tried entering the 6th leaf as being only 1" long (which is less than the length of the clamp), and it claimed that would produce a spring pack of over 1 million lb/in!
However, I think it is OK for calculating one leaf (except there is no way to account for the tapered leaves); it just isn't adding them properly. Note that with the original springs, only the master leaf is .22 (.219 by the book). The other 5 are supposed to only be .188" thick.
I measured 3 original springs, and got values from 110 to 145. The 145 was pretty rusty, so higher friction between the leaves likely played a role. The replacement spring came in at 222! Here's a shot of my lashup to check spring rate:
There is a second needle valve that isn't quite visible (hangs down behind one of the support bars). It and the one that is visible allow adjusting the amount of air inside the cylinder, while the gauge reads the resulting pressure. Since I know the area of the piston, I can calculate the force applied to the spring, and measure deflection with a handheld ruler (not shown). I took two sets of measurements, one with the spring rising and the other falling, and averaged them for the final calculation. Hopefully that eliminated or at least reduced the effect of friction between the leaves.
Here are the specs for the 208636 spring