1) When using the I/Q recorder the scale factor is not recoverable, so you will have to use the data as full scale if saving as 16-bit ints. If using the API you can store the scaling factor separately and use it to convert to dBm if needed. The reference level being used as the scale factor does not apply with the I/Q recording utility.
2) Check out the docs for more information on scaling, we use this approach for both our BB and SM line of receivers. I/Q values have a similar scale as a voltage, but need additional conversion if you want to use them as a voltage.
https://signalhound.com/sigdownloads/SDK/online_docs/bb_api/index.html#IQDataTypes
Andrew