I think Putin is all in on this one. Whatever happens, he needs to be seen to win. I dread to think how this is going to end.
He told Macron in no uncertain tones the Russian military was staying in Ukraine until the "task" is done, he doesn't seem to have any intention of backing down and I think Macron is starting to realise he was played for a fool.
To be all in means firing nuclear weapons, he does that, he does not win, nobody wins.
Russian psyche, at least those stuck in the past, do not see nuclear war as "the end" like we do - they spent a lot of efforts in the cold war era preparing to survive and rebuild post all out nuclear war and I suspect Putin's advisors are still telling him that level of preparedness is ready even though that is no longer the case.