For the classic single OPAMP differential circuit:

to have good common mode rejection, R1/Rf must equal R2/Rg. When capacitors are involved in the input circuit, you must consider their impedance so R1 + a series capacitor becomes Z1 and you must add a series capacitor to R2, unless the capacitive impedance is negligible with respect to R1 at the lowest frequency of interest.
If you hav capacitors in series with both R1 and R2, and split Rg into two resistors each of double its value as a potential divider between +3.3V and ground, it maintains the same Thevenin equivalent resistance for Rg, but biasses in+ to mid-rail, allowing the OPAMP to function normally.
Input clamping is left as an exercise for the reader - if R1 and R2 are large enough your OPAMP may not even need it - see datasheet for details of what input protection it may have built-in.