Guam doesn’t make sense as a target unless Kim thinks he can defeat South Korea on the ground — which ain’t happening.
Actually, SK is a rather easy target for NK. A few years ago, the brief was 4-6 days, even without using Slime.
US defense and reinforcement plan, without Nuc, is non-operational. US forces there are simply a tripwire.
Kim’s problem is not taking SK. It’s what to do with it once he did, so he never will. He wants nucs and delivery system so world will give him more bribes not to fire them, as US did for decades.