In my uneducated opinion, North Korea has no desire (or plans) to start a nuclear war with the US. As you said, there would be no good reason for doing so. It’s all about deterrence.
Think about it. The US topples the Taliban. Then Saddam. Then Gaddafi. Kim Jong-un knows he’s on the list. George W. Bush told him so (the reckless Axis of Evil speech).
From his point of view, Kim would be foolish not to come up with a meaningful deterrent.
Here’s an idea.
Instead of blowing up, starving and irradiating his own people, he asks for a peace treaty.
Gosh. That’s so hard.
I’d send him some Oreo cookies if he’d sign a peace treaty.