Yeah, yeah, I know. Everything is black and white and certain in your mind. No room for complexity or surprise. We are definitely going to war with Russia, it has almost no chance of going nuclear, and there is absolutely no chance we could find wiggle room with Article 5 if push came to shove. Nobody has ever done anything like that before in all of history. Certainly not even some of our NATO Allies when we invoked Article 5 after 9/11.
I think your own view seems kind of black and white. You say about NATO going to war with Russia but if Russia attacks a NATO nation and NATO then fights back, then I'd say Russia is going to war with NATO, not the other way around. I say your view seems to be black and white because your reasoning seems to be that if Russia attacks say a Baltic country, then NATO fighting back would constitute "going to war with Russia" and that would likely lead to nuclear war. I do not buy that at all, either that fighting back constitutes going to war with Russia or that it likely leads to nuclear war. As for those very smart people you mention who have said such, I'd be very curious to see the reasoning they use to reach such a conclusion.
Also, why do you presume NATO would have to push into Russian territory to defend NATO? Considering the industrial capability, logistic capability, training and equipment superiority of NATO, all NATO would need to do is:
1) Destroy all Russian aircraft trying to attack
2) Make all Russian tanks go boom
3) Kill all Russian infantry
Yes NATO forces might need to advance some to hit Russian artillery, but then they could go back. If Russia tries attacking again, the same thing would be done. No need to advance into Russia itself.