The listed firing rate is a speed multiplier for longswords. The real rate is 2.2 hits per second (0.45s to hit once). This is because the firing and charge rate of melee weapons often gets skewed due to attack animations.
On Update 7.8, the Cronus Blueprint was only a guaranteed reward the first time Tolstoj is completed and the chance for it to drop exponentially decreases each run afterward. This was put in place to prevent credit farming. This was then changed, as weapon drops are now obtainable by chance upon completing Assassination missions along with the Warframe component drops.
The Cronus blueprint drops as a pink orb when Vor is defeated.
Only drops if the player who killed Vor had a conclave level below 400.