Seems to me he's stuck in the mentality of the Cold War, he says that he still see things in that same way, which is totally typical of older people, being unable to adapt to revolutionary changes. Later in his life Einstein refused to accept certain results in physics, as smart as he was.
Yes, the USSR had a "sphere of influence", but now they're the 11th biggest economy in Europe. Their only hope seems to be threat of nukes, and if counties refuse to negotiate with the terrorist Putin, he'll have to take the land he wants by force.
If he does launch tactical nukes, the US will likely use conventional weapons on Russian forces and cause proportional destruction. I don't see how that helps Putin, unless the horror of it all causes populations to decide to surrender to Russia. Otherwise you get no advantage and escalation leads to mutually assured destruction.
Putin can end the world any time he wants; if he wanted to, you'd think he'd have done it already. Sadly if that's his goal, then that will happen (unless someone in the launch command chain stops him). In the meantime, he seems to be keen to keep the US from intervening, and I think they'll keep from using nukes, as it would likely not play out well.