He's cutting off Russia's nose to save his own face. I'm not sure his sycophants will remain loyal
Nukes are a bridge way too far... and there're not even practical on this battlefield.
It is critical to remember that while they are physically smaller than strategic nuclear weapons, tactical nuclear weapons would still mean wide-scale death and long-term human suffering. There is no exact agreed-upon definition of what size constitutes a tactical nuclear weapon, but they typically range anywhere from 0.1 to 50 kilotons. For reference, the nuclear bomb the United States dropped on Hiroshima in 1945 was about 15 kilotons — the effects of which continue to be felt to this day.
Russia would become a global pariah if it used these... even in China.