Your links don’t even come close to what you claimed and his statement was about not using nuclear weapons against non-nuclear powers that use bio or chemical weapons.
So tell me again why you think Putin wants to commit suicide by just suddenly deciding to end it all by attacking the nuclear NATO powers of the U.S. France and Great Britain, and face the conventional forces of all 28 of our nations?
I don't know where you read that.
I only said that he is cornered, and a cornered animal is not predictable.
I don't think he would do a first strike as Russia would be destroyed, most of the US's urban centers are already destroyed - Detroit, Oakland, Newark, Philadelphia... our own fifth column took care of many of their potential targets.
The problem is, humanity has a habit for sliding into war... remember FDR - "NO FOREIGN WARS" and a few years later American boys were dying on foreign battlefields.
We don't need a first strike, just a single miscalculation.
An Archduke Ferdinand Moment, a Gulf of Tonkin... a spark and the rest goes on autopilot.
Some people do think Putin is mad enough to try it - some credible people: If Putin goes nuclear
Putin's nuclear option
I cannot find the original article where I read the quote of Obama stating that he would not respond to a nuclear attack in kind. I redact it.