I don't think it is sensible at the moment to take into account what Putin says or has not said. It is obvious his words have no resemblance whatsoever to his actions. He does not need excuses to attack other countries.
Not intervening is a sure way to have delayed consequences from same aggressor, of same or worse manner. This isn't about Ukraine itself anymore, not with Russia/Soviet history of dominance, coercion, bullying and murder. Nothing has changed in the leadership, not for the better at least.
I really don't get people who are naive about Putin. He is extremely clear in his communication about his goals and he just started yet another phase of realizing them. For those won't bother going through them - the goal is pre-1989 setup at least within Europe and near east. All the countries formerly enslaved by Russian communism in some form have very strong objections, and well the rest of free world seems to agree.
Putin has a proxy - Belorussia, controlled by a same-type ageing dictator Lukashenko. He is doing a military mobilization right now and has borders with Poland and Baltic states.
Belorussia attacking a NATO country ends at best in it being occupied by NATO, at worst in the same war between NATO and Russia that Putin don't want in the first place.
Armenia is a member too, but Putin didn't help them in Nagorny Karabakh, saying it was Azerbaijan territory by international law. I beleive it was a demonstrative punishment for Armenian 2018 "velvet" revolution.
Kazakhstan is a member too. Putin used his army in Kazakhstan in January after Tokaev said that protesters are supposedly foreign terrorists.
Putin will not directly help Lukashenko against NATO countries on their territory, but is well capable of throwing his army to "protect" Belorussia from retaliation, including anti-air warfare.
This. A way worse result for Putin than Ukraine slowly becoming NATO-aligned is a sudden NATO-enforced regime change in his other (and currently reliable) European buffer state.
Putin cannot really do much. West fully joining the war would mean nuclear exchange. But Puting ending the world due to weapons shipments? Very unlikely.
