With all respect to you (and I have enjoyed your comments in this thread) I feel like you're ruminating on the worst case scenarios and hype, and maybe not listening to reason?
Don't forget mate, Russia has been threatening us with nuclear weapons for more than half a century, it's part of their playbook. I'm not just talking about in the 60s and 70s, but as recently as 2008 they
threatened Poland with a nuclear attack over NATO matters, this wasn't the first time and it won't be he last.
I recently watched the docudrama 'Chernobyl' - this will seem off topic for a moment, but bear with me. In one scene, Gorbachev tells his ministers that "our power comes from the perception of our power" - now I've no idea whether or not he actually said that, but regardless, it's absolutely true. Strongman bluster, nuclear sabre rattling, powerful arms projection - it's always been part of Russia's games on the international stage. The only difference is that right now the rhetoric has been cranked up to 100 because Putin is under the international spotlight.
Never forget the facts - 1) NATO is not getting involved in Ukraine. 2) Bluster aside, Putin is no closer to starting a war with the rest of Europe that he can't win, 3) Even if those health rumours are true (and we've no reason to believe they are because Ukraine has been an ongoing point of contention for nearly a decade) would he want his legacy to be the leader that caused the utter defeat of his country and possibly destruction the world? It's really, really, not going to happen.