Getting output voltage after connecting snubber across Triac
You aren't going to get it down to 0V. The capacitor will leak some amount of current by it charging and discharging. That current will create a voltage drop across the load. You can reduce the voltage by reducing the resistance by adding a resistor in parallel to the fan.

Reducing the capacitor will defeat the purpose of the snubber, which is to reduce the voltage spike on switch off of the inductive load. So you are working with a lower limit on the size of the cap you should use.

If you actually want the voltage to be exact 0 then you need another switch between the snubber and the load that closes sooner and opens later. The switching current on that one can be lower because the snubber will restrict the current after the main SSR is off.