...well, we sorta know just based on logic that scenarios like 'china uses small nukes on rogue terrorists' are pretty much bullshit. and we sorta know based on lots of history that nukes being used is kind of the very last thing that a country would do to protect itself, and it may not even use them in that case simply because once it's done they are now open to the same attacks.

true, we don't know what will happen in the future. but we can make an educated guess that nukes either will never be used again, will be used but only by rogue and irrational actors, or will be used again leading to the annihilation of many countries (unlikely), again using only logic. and if you haven't noticed, preventing option 2 has been the focus of intelligence operations the world practically since nukes existed, so it's not like nobody has thought this out.