So, should the world pull the lever and save Gaza, knowing it will ultimately lead to more Israelis dying? Or should they keep giving them more weapons, so that they can keep murdering Palestinians with them?

Sanctioning countries that send troops/bombs into other peoples countries till they stop doing that and repay for the damages would be a way to prevent that. They can still have guns for self defense, but as soon as they use them to retaliate an not just defend they get cut off. (Of course this system can be beaten, and it also requires a world police force, and the UN has never been that in what I assume is partial design, the UN should never be able to threaten the USA/Russia).