The fact that the pins are listed by name in the package spec, but not further defined, indicates to me that they're either ports for automated end-of-line testing or for diagnostic purposes. Less likely, but quite possible, is that they're special purpose functions such as fine adjustments or reference voltages that are used only internally or by a few select customers. In any case, the only advice given is on page 4, where they're listed as no connects. I'd take that to the bank, as it's possible that some connected conditions could damage the sensor.
The transfer function you listed agreed with the one on page 5, and matches the graph as well as the specs table. Since it's directly proportional to Vs, if you want good accuracy you should regulate Vs pretty tightly, or alternatively use Vs as a reference to your ADC if you're digitizing the output.