PSRR and CMRR in a diffferential amplifier
The PSRR should probably be measured in terms of the differential output, \$v({\rm out2})-v({\rm out1})\$, rather than a single-ended output.
In a real circuit, the PSRR depends mainly on mismatch between the components. To estimate what this design would produce, you should include some mismatch between R43 and R44, and between M327 and M328. In ADS is fairly easy to set up parameters with tolerances and do monte carlo simulations to see the range of effects with process variation.
You might rather do an AC simulation instead of transient, so you can see how the PSRR varies with frequency.
Voltage sources add when placed in series. It would be slightly more obvious to others to just put your AC voltage source in series with the DC source than to make a new source with both AC and DC components. But what you did won't give wrong results.