Is my Precise Capacitor Ratio Repeatable?
The 1% capacitors have a ratio accurate to +1.92/-1.89%. 

Possible variation in the input capacitance of the switch is hard to estimate without more knowledge of the processes, a WAG might be 10-20% of the nominal value to 2-3 \$\sigma\$. At 20% it would be adding +/-1.2% to the error. 

Maybe consider using a lower capacitance switch such as a USB switch- some of them are in the 7pF nominal range. You may also see some variation of the switch capacitance with voltage which could cause some distortion of the waveform. 

Of course whatever you have on the other side of the switch is going to add to the capacitance etc. 

Good C0G capacitors should have negligible voltage coefficient and should be very stable with temperature (&lt; 30ppm/K) and time. Do check the detailed information (not just the data sheet) from your proposed supplier.