Flo,
1) If I read that correctly, the gain of your amplifier is 1000 volts per amp. So I would think you would convert the SA44B noise measurement to volts per rt Hz, and then use this as your noise measurement (mA/rt Hz because amp output is 1V per mA input).
2) You are using power averaging, so there is not a 2.5 dB correction to apply.
Also, please note that if your gain was 1000V / V, this is actually 60 dB of gain, not 30 dB. (20 dB gain = 100x power increase = 10x voltage gain)
