If Kim is serious about a deal, how would he ever be able to trust any assurances from the USA under Trump? The USA has lost all of its moral high ground and credibility as a principled player whe Trump runs around smashing alliances with every tweet.
The only thing I can think of is China backing Kim if the US reneges. I don't think China, SK and Japan would stand for unilateral military action against the North, so that would leave sanctions which would also need those country's support. NK is in a much stronger position in this respect than Libya was.