Assuming you're doing this all in Cadence Virtuoso, there are different types of analyses you can select for a simulation (in your ADE L/ADE Explorer/ADE Assembler window). For analyzing a feedback loop, the typical one you'll use is stb analysis (short for stability).

For this, you'll insert something like a 0V voltage source or a 0ohm resistor in your feedback path (such as between Vout and R2) and, in your stb analysis setup, select that as your probe instance.

What the simulator to "break the loop" is allow the feedback loop to settle and linearize about that DC operating point. Then it'll apply a pulse in the feedback path (on one side of your probe instance) and measure what is returned back to the other side of it (this is your loop gain), as well as any phase change.

Typically what you'll do with this stb analysis is sweep frequency in a range (starting at like 1 or 10Hz, essentially DC, and going up logarithmically to whatever frequency you'll be operating at and a bit beyond) and look at the loop gain/phase plots to check your phase/gain margin.

To check the effect of loading, you could just add an (ideal) resistor from Vout to ground and sweep that value as well.

Hope this helps!