That’s not correct. Look at Hiroshima and Nagasaki now.
Again, this is not true. Sure a large number of people die, but people are born and fill the gap. There are millions born every day. The land area affected by a nuclear strike is trivial. What are a few square miles or even tens of square miles out of millions. And, as Nagasaki and Hiroshima show, the land can be cleaned.
The other thing you’re missing is that people will take advantage of your unwillingness to use nukes. To show restraint, you have not show restraint in some cases. How do you know if someone can kick your arse if they never actually kick anyone’s arse?
I’d have used nukes in the Korean War, Vietnam, and Iraq. Indeed, that nukes were not used against Iraq was a huge indicator that Iraq did not possess WMD.