Pole and Lithuanian... Germany should be prepared to be a next stage, together with Romania.
Do you realise that the four countries you mentioned have larger population than russia and, apart from Lithuania, relatively large and well equipped armed forces? Taking into account the performance of your army against Ukraine I wouldn't have high hopes of a successful russian attack against East Flank NATO countries. As a matter of fact, if it wasn't for your rusty nukes and the distant possibility that some of them might actually still work, East Flank NATO would wipe the floor with your slanted-eyed rapists
easily.
20-year "catch-up" infusion of capital
EU funds were, of course, important, but prior to 2004 Poland wasn't doing too bad either, after throwing off the communist yoke. I'd say political, economic and legal stability, combined with traditional Polish resourcefulness, were the main factors in our success.
this would be a very difficult sell to Russians (...) Russians have a very high savings rate (...), and the state constantly runs budget surpluses
This might be the case, but still russia has lower GDP per capita and even exports per capita (despite being a huge gas station!) than Poland...
en.wikipedia.org/wiki/List_of_countries_by_exports_per_capita
... high stability that the EU brings and foreign investments connected with it are
invaluable. If you can't sell that to your population but can sell dreams of an empire instead... well.