Nuclear weapons in the modern world are useful deterrants, and that's it: a dictator with nuclear weapons has no external enemies they could consider targeting without guaranteeing total annihilation in response.

The one exception here is that using a nuclear weapon on your own country and people might be a useful exercise of power...but even then, it's abundantly clear that the most likely outcome is still total annihilation - the world won't tolerate a nation lighting off nukes against targets in it's own borders much either.

Why do you think so? Famines seem to work just fine within borders.

I'd argue that nuclear weapons are no less safe in representative democracies. The only country to use nuclear weapons against another nation was a representative democracy. The only country to use nuclear weapons against another nation multiple times was a representative democracy. The only country to use nuclear weapons against civilian targets was a representative democracy.