My turn. Russia is essentially Putin.
Of course no. Putin is not a Dark Lord who rule the Army of Zombies by a powerful magic. He is just a man. Expendable as everyone else.
If Putin calls for a nuclear surprise attack on the US, his military has two choices.
No. Putin doesn't "call" for a nuclear attack. He just "give permission" to do it.
Obey or assassinate. If they obey and find the US alerted to the attack (they have expected and planned for this for 60 years) the US will immediately launch their land based missiles at the Russian military before they can be destroyed.
No one can blind America better than Americans.
Ukraine (as well as Poland and Germany) is not really vital for the USA. If the US decision makers believe that there is actual preparations for the Russian attack - America will make few steps back to defuze the situation. The almost only situation in which they don't do the step back - is when they actively denie the facts they see, and count them as a bluff or something.
Bombers in the air and boomers at sea will attempt to destroy the remainder of the Russian military and decapitate the Russian elite, military and civilian. There will be no time for a moratorium.
Of course there will be time. Read American nuclear posture and US Constitution. Americans are more interested in the saving american lives rather than in killing some random Russians (for Russian elite is already in the shelter under Yamantau mountain, and America doesn't posses thermonuclear cumulative warheads to reach them).
If they assassinate Putin they keep their privileged positions and become heroes. What would you do in their place? Can Putin be sure of what they will do?
You watch too many bad movies. It is not the way how the things works. Good commander doesn't sent his forces. He unleash them.
Did you serve in army?
A bit exaggerating, one can say: "In the Army, everyone, up to the 1st lieutenant, must be able to work and fight by themselves. Captain must be able to organise their work or fight. Major must be able to clearly report what is happening. Lt. Colonel must be able to find the place were to put his signature. Colonel must be able to sign where they tell them. General must be there, where they bring him".
As one of our Generals once said to one of his subordinates, who tried to play a great tactician: "The battle planning is very easy - you just paint red arrows over blue eggs. Why, the f#ck, you have blue eggs in one place and the red arrows in the different?!?", and, of course, all those eggs and arrows are not painted by the Generals nor the Colonels themselves. They are painted by the Lieutenants and Sergants from their stuff, who paint them according Field Manuals written by other lieutenants from the higher staff.
Same way, when "Ukrainian" UAVs attacked strategic bombers, nobody (including Putin) started thinking "What should we do now?" The heads of the MoD, SVR, FSB, other organisations, just got from the shelves preplanned and already signed files "The actions at the level of the deniable proxy attacks against strategic nuclear forces", and act accordingly. In the case of "extremely provocative actions" they just took another file named "The Special Operation of Strategic Deterrence Forces" and act accordingly. Putin's role (or, to be more accurate, the role of ministry of foreign affairs, ministry of economic and development and civilians from President's Administration) is not to block those actions. And he simply can't block those actions without proper reasons. It is the system. You try to act against the system, whoever you are - you are a deadman. Something like what has happened with Eltsin after his attempt to stop the march on Prishtina.
Anyway. Of course, nobody will launch a nuclear attack just out of "caprice of a dictator". It will be launched as the lesser evil, when there is the difference between say, one million killer and sixty million killed. Like it was demonstrated in the classic "Dr. Strangelove" movie.
(With the obvious difference that it is not dialogue for a war room, it is the dialogue for the younger and aggressive technical personel aka back room boys).
The choice is - if they launch the attack, they (both generals and back room boys) have a good chance to survive and become rich and powerful. If they don't attack - they will be killed by FSB or by NATO soldiers.