I second ST-One's opinion here. The Narada wasn't doomed, it had already survived travelling through a black hole before. Would it have been a responsible command decision to let a hostile vessel with bad intentions potentially escape further into the past where it could not be stopped?
If that was the case, why even bother offering assistance if Kirk knew the Narada would survive the trip? Did Kirk not say, and I quote:
"Your ship is compromised. Too close to the singularity to survive without assistance which we are willing to provide."
If Nero knows his ship can survive the black hole, why were all the Romulan crew members scrambling around the ship like it was doomed? And if the Narada can survive the Black Hole, why does Nero tell Kirk that he would rather face agonizing death than assistance from him? Wouldn't Nero just say nothing at all if he knew he was going to survive?