Hiroshi,
I’m glad you like it!
1. Yes. Remove the 20 dB pad after it has been measured. We use the 20 dB pad to measure both high gain and low gain and compute an internal offset.
2. Make sure you don’t exceed +20 dBm into the SA44B. You will need to compensate your measurement for the additional gain after the store thru, but otherwise it should work just fine.