The North Koreans aren’t going to agree to unilateral disarmament.
If they have to get rid of their nuclear weapons, they will want side guarantees for their security from China and Russia.
They will never agree to allow the US to oversee a denuclearization process.
If the US won’t compromise, Kim will take his chances and ride out the sanctions.
He won’t put his own country at risk. Neither would Trump.
He would do it for a ratified treaty.