To clarify, I'm not trying to make any persuasive arguments about this. This is based on my own calculations, and there is generally not enough publicly available information to come to a fully informed verdict. For example, if you take all figures by Hamas, including some of the low number of deaths of their own fighters they reported, the ratio climbs up to 4:1 or more. I doubt anyone can say with certainty what the right figures are (well, perhaps some can provide good estimates, but not publicly).

I'd be interested in knowing how the IDF mandate to destroy Hamas is defined concretely in terms of KIA of enemy combatants but perhaps that hasn't even been decided yet.

I see no reason for Israel to "back off" before the hostages are returned and Hamas surrenders. Like all wars, it will probably end when one of the combatants surrenders. Hopefully this will happen soon.

But if you look at it in terms of civilian casualties, they've gone down massively since the start of the war. Israel "has" backed off in many senses of the word.

The problem is that Israel hasn't left Gaza, because despite your statement that the entire Hamas command staff is dead, it seems very likely that the minute Israel leaves, Hamas regains control of Gaza and starts building up strike capability again. So we're in a semi-holding pattern.

Now, there are good questions about why we're in this holding pattern. Many people (including me) think that it's because Netanyahu isn't trying to actually "win" the war, but prolong it, so this situation is good for him. Hence no steps to leave and set up a Hamas alternative, but also no move to more decisively finish the war either. A holding pattern suits Netanyahu just fine, at the expense first and foremost of the Gazan population, but also of the Israeli population (and also the Israeli economy, reputation, etc).