After staring at wiki pages for a few minutes, I don't think that's the right formula to use. It says 2x weight for candy drops. Does that mean +candy drop combined with +item drop gives that bonus? If so, there are two terms needed (2*weight fairy formula for candy - 1*weight fairy formula, which can likely be simplified). Otherwise it should be 2*weight formula, probably.
Someone that cares about this getting added should figure that out.