Nuclear war is a HUGE step up from any of the previous steps. Like you could build a binary system based on those principles, with Nuclear War being 1 and the rest being noise that's equivalent to 0.

The only way he'd entertain it is if he's truly lost his marbles, and if that's the case then this timeline just got a whole lot shittier regardless of whether we capitulate to the madman with the nukes or not. I sincerely doubt western institutions are going to show their bellies because of Putin's nuclear threats, so we'll see if he's bluffing one way or another.