@Arc7Kuroi; no, I still don't think that we should be using the Bankai multipliers for that ability of Gin's sword.
I'm just addressing the issues with a different part of the proposals in the OP.
I'm pointing out that the timeframe is no longer a constant once Toshiro starts moving away from the sword and the sword is being moved from its original trajectory. The calc assumes that Toshiro completed his motion after Gin's Shikai only moved 2 millimeters. This is obviously not true as Toshiro's head would be further away by that point, and therefore the sword would have a longer distance to cross, which affects the timeframe.