Quick question about the L200 circuit limit
Yes, the term given is the voltage at pin 5 minus the voltage at pin 2 (the datasheet's typesetting does not make this clear). The L200 is measuring the voltage drop across resistor R in Figure 2 to determine the current limit set by the internal comparator. Given in the datasheet is \$V_{5-2}\$ is a typical value with a temperature dependence given in Figure 18.

The explanation of current limiting given in the ST Designer's Guide on pages 3 and 4 is much more straightforward, using \$V_{sc}\$: the [short-circuit] current limit starts when the L200 sees about 450mV between pins 5 and 2. This avoids the error in typesetting later repeated in Figure 5 of the guide.