You need WiFi active, but not the Spark cloud, so I am not sure what you are seeing.
Once a minute sounds right but it is programmable in the TI CC3000. There is no “easy” interface to change the period and the TI part has a limited number of write cycles for certain parameters that are stored across power outages so you don’t want to change it often.
In my experience the RSSI values can vary core-to-core and with small physical changes like putting your hand between the antenna and the router. Folks have tried location based code, but I think it would be very challenging to use the RSSI values for anything but simply finding the strongest current SSID signal.