Opamp phase shift compenation
First things first. You need to stop asking for insane levels of accuracy. Sure, your Spice package gives phase measurements with a resolution of 0.9 micro-degree, and group delay resolution of 1 psec. Do not pay attention to this. When measuring 50 Hz phase, for instance, your 38 mdeg corresponds to 2 usec. Do you really care about microsecond differences? If so, why? And consider that your real-life components will probably be 1% resistors and 10% capacitors, so the equations which produced the numbers really cannot be used at this level of accuracy.

With that in mind, tell us a) what accuracy you need, and b) what accuracy you're getting. "more than that" is not remotely useful.