Regarding Kw, titrations, and pH
When using a pH probe, instead of aiming to reach the equivalence point of the titration, you should be titrating beyond it to create a complete titration curve. With an indicator, the end point is clearly indicated by a color change; with a pH probe, however, the end point is indicated by a steep change in pH in a plot of the data, thus requiring the collection of data beyond the end point.

While in theory the pH at the equivalence point of the titration can be calculated (and, for the limiting case of a strong acid and strong base, is exactly the $K_w$ that corresponds to the temperature of your solution), calculating the pH at the equivalence point and aiming to reach that pH is (i) bad lab practice, since if you're able to calculate the pH at the equivalence point, you're presumably trying to experimentally verify theoretical calculations, and (ii) not applicable to your current experiment, because the organic acids present in fruit juice are weak acids, whose conjugate bases are weak bases that will raise the pH at the equivalence point (and render the pH impossible to calculate for your purposes).