Am I overreacting

Yes.

Totally understandable in the world with the dopamine fueled news cycles running on fear.

But, nuclear war is very unlikely, that’s why Putin is threatening it every other week, he knows he won’t do it, and other leaders know that too. It’s meant to terrorise people.

Help Ukraine to grind down russia so that eventually we can denuclearise them (remove the Kremlin and let the russians have another try at democracy would be nice too) is IMO the closest any regular person can do today.