1. UN? Nope. The last time the UN did uphold its charter was, ironically, in the Korean War (gulf war 1 was UN approved because of the oil all the main UN nations depended on).
2. Without a question, more. Exponentially more. The south korean capital wouldve been anhiliated before the UN forces even landed in korea. Remember NK has thousands of high caliber artillery trained on it. Plus they also have nukes and biochems.
3. Support from the world? See #1.
4. no doubt, yes and hell yes.