Does Passimian's "Throwing Coach" Ability work if my Active Pokemon's attack doesn't do any damage to the opponent's Bench?
No, Throwing Coach only adds +30 more damage when you actually do damage to your opponent's Benched Pokemon. In other words, you have to do some bench damage in order to have "+30 more" done.
Source: Chilling Reign FAQ; TPCi Rules Team (2021-06-17)