The question is, "Is he bluffing?"

I think he will use whatever weapons he has, but whether or not his generals will follow orders is another question.

His generals know that if he launches a nuclear strike, Russia could be destroyed. Not only due to a nuclear strike in retaliation but by being ostracised by most of the world.

If we allow his threats to stop us from supporting Ukraine, then other state actors, like North Korea, etc., will also threaten the use of these weapons.

The use of these weapons will also kill many Russians. Not only soldiers on the battlefield but Russian citizens as the fallout drifts over Russia proper. His generals know this, and I don't think they want to die or be held as war criminals.

Only time will tell.