Why does Jupiter break comets apart?
It is.  Tidal disruption occurs when $\rho_{Jup}(R_{Jup}/R)^3$ > $\rho_{comet}$ where R is the separation and $\rho$ is the density.  The density of Jupiter is 1.33 g/$cm^3$ and the comet was estimated to have a density of only 0.5 g/$cm^3$ based on the radius at which it disrupted.  That is, disruption took place at separation R ~ $(1.33/0.5)^{1/3} R_{Jup}$.