Hello Gennady,
Let me address your questions.
1. Yes, Rp is meant here.
2. The full range of Rp is 798 to 3926991 Ohms. Setting Rp MIN and MAX values, you limit the range to the region of interest, and the full scale now runs from Rp MIN to Rp MAX value
3. This value greatly depends on the system configuration. It can be better, it can be worse. The value given is one of the common ones we have encountered most often in real systems.
4. No, this value is dependent on the whole system configuration.