As your circuit is characterized by voltage (and not power) gain, be sure you appy and measure correct sources and loads.
A common practice is to talk about equivalent power levels. for example you can express the input voltage as equivalent power to 50 Ohm load.
To do so, take the 50 Ohm source and connect to 50 Ohm resistor. Take the input voltage and convert it into differential using voltage controlled voltage sources. Use these voltages to supply the Mixer.
Check that the input voltage is what you expect.
Similar you can do for your circuit load, if you're interested also in voltage to power conversion at output.
Be aware if you simulate noise!
The bench is a little different and depends on noise quantity you want to calculate.
I hope it can help.
Mazz