So you are actually asking about simulated "measurements".
There are two points to consider:
- you need to understand the nature of small signal AC analysis. Voltage levels are meaningless in small signal, they aren't but scaling factors. Selecting a source voltage of 1 V has the advantage that output voltages can be directly read as gain numbers.
- to get right loop gain, the amplifier must be correctly biased. A smart way is to do it in a feedback setup that achieves right DC operation point but doesn't affect the loop gain.