I think you're contemplating the possibilities if Russia resorts to a tactical nuclear weapon. But you're still avoiding the question of Russia using a nuclear weapon on the Ukraine, which would be the most likely of possibilities.
As to Russia using a nuke on Poland or one of the surrounding Nato countries, your military mindset has to be suggesting that MAD is not inevitable.
My opinion remains, that the use of a tactical nuclear weapon that doesn't violate the mutually agreed upon rules of the war, would not trigger a full scale nuclear war.
Does America have an option for the use of a tactical nuclear weapon?
Does Russia have an option for the use of a tactical nuclear weapon?
These are questions in a discussion that propagandists would rather not be asked.
Are you of the opinion that MAD isn't inevitable? Your anger seems to be taking this conversation between us to a new level. That's telling.