RC Snubber For Phase Angle Controller
The edited question is clear, now.  The capacitor is correct WIMA MKP 250VAC is the correct choice.  The resistor could be under rated, also it seems a little bit too low 360 ohm to me. 

Have a look here: RC snubber circuit design for TRIACs - STMicroelectronics , there is a calculation for 26W pump and the calculated sbubber is 10nF and minimum resistance of  620 ohm. I wouldn't change the capacitor you've got, it's really high quality and for this specific task.

Choose a capacitor for higher voltage, like WIMA MKP 630V 

Also, BTA-16 is somehow too big for the required load, if you can change it use a smaller one like BTA-06.