I think you fail to realize that Ukraine is Russia's backyard. Its key strategic defensive area for Russia. Any kind of Western invasion of Russia would have to happen through Ukraine and they will be extremely sensitive about it.
How senstitive? Well they can just bomb the shit out of Those nato forces and then say well, what are you gonna do now?
Russia cares more about Ukraine than Nato does. So, nato then has to make a choice. Russian attack on Nato forces did not happen in Nato soil. So, there is no threat of a Russian invasion towards nato, no need to trigger article five either. So, Nato has to essentially choose to start world war 3 for a place like Ukraine that they know is already in Russia's backyard.
Nato with their 40 trillion dollar GDP economy starting a nuclear war with Russia with 2 trillion GDP is actually advantages Russia. They have less to lose but can do equal damage to Nato cities.
So, Nato will back down and swallow that loss. Just like Russia did when US forces attacked wagner in the middle east. Again same problem, They don't care enough about Syria to start fighting America there just to take revenge for Wagner losses.
if they attack you in a place you don't care about. Would you start a world war just for you pride? Or would you swallow the loss? I think you would swallow the loss.
So, in a so called stare down contest. Russia would win by killing those staring down and daring the enemy to fight back. its just punching your opponent with a gun in your hand. Yes, both have a gun, but the rich guy would probably avoid starting a punching match with a poor guy with a lot less to lose.