I can't speak to the actual range of the units in feet, because I am just starting out myself. But here is what I found out about reading the current being drawn:
My modules are being powered thru LM2937ET-3.3 regulators, from a 12 volt power supply. I put a 1.0 ohm 1% power resistor in series with the 12 volt input so that I can see the voltage across it with my scope. But there was a bit too much noise on the signal, so I changed from the switching type of power supply to a linear type of power supply (one that has a transformer in it that mostly isolates it from any noise picked up thru the ac line. Using batteries would work too.
The scope showed 222mv across the 1 ohm resistor in varying increments of 100's of microseconds. It looks like the module switches to the transmit mode and out of it very fast. Only long enough to send the data stream. That's why ammeters don't show it. 222mv corresponds to 222ma across the 1.0 ohm resistor. I can notice a change in that voltage when I change power levels on the transmit module.
My receiving module, sends data to my application and the application reads back the RSSI value. But I haven't noticed any appreciable changes in the displayed RSSI value when I change the transmit module's power level. So that is perplexing.