You perhaps recall the phrase" "Fire everything"? Nero's previous sucessful missile attack had punched right through the Enterprise's shields. Had Nero had anything left to hurt Kirk with, however feeble, I'm sure he would have used it. So we are left with a completely defenceless Narada. But you say, perhaps he was playing possum. That turned out not to be the case, though Kirk, despite sensors, may not have known that. But then why offer help in the first place if he wasn't confident of his safety? You seem to be saying he wouldn’t or shouldn’t take that risk.
"Fire everything" was aimed at the jellyfish, before Enterprise's arrival. They fire about a dozen torpedoes, no energy weapons. I don't see any reason to assume they had no weapon capacity. (ETA by this I mean that "Fire everything" can easily be read as "Full spread, maximum yield" rather than "Empty the phaser banks and torpedo bays completely!")
As for offering help, as I said, they're compelled to provide it if Nero is prepared to accept it. They can hardly just guess
that he isn't.
Do I? So you are saying that, as a principle, if someone's death is inevitable, it should be ethically OK to kill them, irrespective of that person's ethical status? I would caution you to think about that before answering.
All our deaths are inevitable.
You're ignoring the stipulation that the person is actively indifferent to their impending death.