Can you banish this after activating to prevent your monster from being destroyed? I think that the destruction check happens during damage calculation so I am not sure how this would work.
Well, you would activate this before Damage Calculation, and thus it would go to the GY before the actual battle. So, yeah, I believe it was the entire point to use this, then block your own monster from dying to burn your opponent.
To my understanding, I believe this card becomes ubiquitous the turn you use it, and thus is affects all your monsters for the turn, maybe? Or perhaps it might help to wait for a more thorough translation.