A question on factors affecting the offset removal of an opamp circuit
Within the limits of the frequency band that you are interested in the "easiest" way to remove DC offset from an AC waveform would be to use AC coupling at the input of your amplifier using a suitable capacitor.

Another possible way is to sample the input AC waveform with a long time constant low pass filter filters enough to pass just the average value of the AC signal. You could then try to use that filtered voltage to subtract the offset from the original AC waveform.

Both of these approaches will self adjust for variation in input signal amplitude and offset. They are not a perfect solutions however because if the changes in amplitude or offset happen too fast they will not be tracked by the long time constants in the respective circuits.