>one second she is (again) taking down in-flight warships, the
>next she's getting punched out of the sky?

They made it clear that she wasn’t phased at ALL when Thanos hit her without using a stone, meanwhile he could wreck everyone else without needing to use the stones. Not only did he use the power stone after that to hit her, he took it off the gauntlet and hit her with it in his hand.

>and how DID tony get the stones off the new infinity gauntlet
>that quickly?

Remember that new gauntlet was Ironman technology. As was the gauntlet that Tony used himself. Could have been part of the plan and how it was designed so that Tony could easily swap the stones off of one to the other in case Thanos got a hold of it.