Say Trump did deal the "bloody-nose" attack, would that actually deter North Korea from retaliation, since Kim surely knows the risks of dueling with the top military superpower with subpar Cold War-era equipment (that may or may not work)?
You'd be surprised how much of many "modern" countries militaries are made up of Cold War equipment or upgrades from. The F15/F16/F18 are Cold War era. Canada is buying some of Australia's surplus F18s when we replace them with F35s.
That said, you'd be surprised how much can be done with older equipment. Yugoslavia shot down an F117, at the time the pinnacle of technology, with "obsolete" radar equipment.
https://en.wikipedia.org/wiki/1999_F-117A_shootdown
Technology is great and all, but how you use it and the numbers you can bring to bear have an impact also.
Or would he go all in, and fire everything he has at Tokyo and Seoul in a last ditch effort to go down in a blaze of glory. But if he does go all in, there's no way China can condone that, right?
Probably not. But neither do they have to allow the US to occupy North Korea. It's one thing to destroy the Kim regime, but I suspect both Russia and China will be very wary of having a US occupied state on their doorsteps.
But whatever Kim does, if it involves returning fire on the US or any US ally, it is surely a mistake.
Whatever Trump does, if it involves starting a war with a target that hasn't fired first then it is surely a mistake. If Trump fires first, I think Kim's best move is to return fire on US targets but not SK or Japan unless units from those countries are specifically and clearly involved. That way NK can still cry for international support from Russia/China against an "illegal" invasion.
If the US doesn't have a rock solid justification for initiating hostilities, Russia and China may well decide to step in and play peacekeeper for the sake of safeguarding their own interests. And while the US military is massive, Russia and China have significantly easier supply lines to a North Korean war than the US does. If I was the US I wouldn't be just strolling into any conflict where there's the potential for those two to legitimately take the other side.
They can pay with their land.
How much is that worth? I can't see a lot of people lining up to buy land that's just finished being filled with depleted uranium, land mines and unexploded ordnance. Assuming the US doesn't just nuke the place.