Calculating scale is as simple as determining the ratio of the dimension of the model to the dimension of the real thing, so the fraction you need to solve is (model dimension) divided by (prototype dimension).
Convert both to the same units of measurement and do your math. Your Cutter is 360 inches, and your model is 2.4375 inches, so 2.4375/ 360= 0.00677 or 1/147. Finding that last number is easy with the "1/X" key on your calculator.
I ran all three just as you listed them and got results of 1/147, 1/149 and 1/151 for the three, which considering all the factors involved is a very close range and gives you a good idea of what you are looking for; around 1/150.
To get detailed, which matters more when you start to scratchbuilding, the factors here would be:
-what a real "30 foot" cutter's length is. Overall, waterline, etc.
- how carefully you measured the model.
- how much Revell cared when they made the molds. They may have "borrowed" the boats from another model. others would know much more than I.
What you really want to do if you are after the scale of the ship is measure something on the hull that you can compare the actual ship to. Because it may be that this kit has boats that are "over scaled" ie too big.
I usually measure two things: the length at waterline, and the largest width (beam). For the Constitution that's easy information to get. Then do your math.
The waterline length is 175 feet and the beam is 43 feet 6 inches, according to wikipedia.
Now I thought that model was advertised at 1/196, so the real things beam is 522 inches, which divided by 196 equals 2.66, or 2 11/16 inches of beam for your model. Hold the hull halves together and give it a measure.
I hope that helps!