This is how you get more nukes in the world. If NATO wouldn't help protect the Baltics, Poland etc then it's pretty clear their only option for long-term sovereignty would be banding together to create their own nuclear deterrence. No amount of training would stop a country like Russia (or the US) from trying their luck at some point.
Russia attacking its neighbors goes back centuries. And for that matter, so does western Europe and the US. If there's no formal alliance, then the western powers would be a threat too.
You make some very good points. But creating and maintaining a credible and safe nuclear deterrent is VERY expensive. I think the trick to convincing people they don't need it is to not go around invading other countries in the first place. Mexico doesn't have nukes despite the US easily having a half-dozen reasons it could trump up for "regime change". South Africa gave up their nuke program (I REALLY need to study this one, it's on my To-Do List). Right now we are witnessing Ukraine shatter the Russian military, a pretty good endorsement of conventional deterrence against invasion at least for everyone else who is concerned.
Russia attacking its neighbors goes back centuries. And for that matter, so does western Europe and the US. If there's no formal alliance, then the western powers would be a threat too.