For Emf detection

1. ( slope, intercept voltage, and dBm intercept ) Are these consistent with the AD8362 datasheet and typical operation?  Yes, in the specification table, you will see typical slope and intercept values at different frequencies. These values will change from part to part. Figures 18 to 25 provide statistical data on these variations.
2. Is the slope of 50 mV/dB a standard or average value for the AD8352 over the frequency range? 50mV/dB is the average value at 900 MHz. At other frequencies it will vary slightly (e.g. the averate at 1900 MHz is 51mV/dB)
3. Does an intercept voltage of 0.0 V correspond to −60 dBm input power make sense, or should I expect a different value based on the datasheet? The specified Intercept is an extrapolation. It is the input power level that would give an output voltage of 0V if the linear portion of the Vout-vs-Pin curves (roughly -55dBm to +10dBm) was extrapolated.
4. How critical is it to adjust these constants for accuracy, and can I rely on these default values for basic EMF detection without a lab calibration setup? It depends on how accurate a measurement you want to perform. Take a look at Figure 25 as an example and lets just focus on ambient temperature (black curves). Pick an input level, say -15 dBm. If you apply -15 dBm to multiple devices, you will get an output voltage that will range from around 1.5V to around 1.7V (i.e. the vertical thickness of the black distribution if you look at the -15dBm slice). In dB error terms, this corresponds to around 3 dB (we get this number by doing a horizontal slice at the same point on the graph. 

Any guidance, corrections, or pointers to calibration recommendations would be great to me? We generally recommend two point calibration, that is apply a low level (say -30dBm) and a high level (+5dBm) and measure the two output voltages. With these four points you can back calculate the slope and intercept of that particular device at that particular frequency (i.e. Vout = Slope x (Pin - Intercept) where slope is in mV/dB and intercept is in dBm). 

Once you have an equation for the behavior you can rewrite the equation as Pin = Vout/Slope + Intercept to figure out your intput level. If you are trying to calculate EMF in volts the equations need to be rewritten slightly. It might be simplest to calculate the EMV in dBV and then convert this back to V.