I'm wondering if you could not use the gradient as an alpha map (opacity) for the candle body. This could be used to make the candle body more transparent in the top gradually going to non transparent. If the light source is the wick, then it should shine through the candle in a convincing way and it would save a light source. It would probably also be easier to set up.
Regarding the Reality translucency option it requires some color math to make it work as expected. I always forget how, because I rarely use it