Most likely, which is why they used toxic gun. We didn't see anyone in this chapter having the weapon on them, so it was probably a back up weapon incase anything happened.
I think that Jack's 1 Billion Berry bounty is based on "how much of a threat he is to civilians", rather than being based on "how much of a direct threat is he to the world government". It is possible that Kings of Zou defeated Jack.
Can't be, the defeat happened AFTER Jack attacked them, that dog girl said before these chapters to the Strawhats that Fujitora and Sengoku defeated them, but that he's probably out there somewhere