When the Congress Poland was created, its king happened to be the tsar of Russia, so there was no danger of Kingdom of Poland trying to claim its former lands. But I agree that Russia might not be happy about strong Poland on its border. OTOH they can not do much about it, except fighting Napoleon who just crushed Prussia and Austria (again). The tsar might settle with a part of Eastern Galicia, possibly East Prussia (just to keep it away from Poland) and some guarantee that Poland renounces any claim to territories that are now Russian.The main potential problem with the above is that while the Russian “establishment” could not care less about the East Prussia (*) it did care a lot about the implications of having a big Polish state on its border: one of the OTL reasons for Alexander’s breakout with Napoleon was Napoleon’s refusal to guarantee that DoW is not going to be expanded. It was fully expected that extended Polish state is going to start looking for the Russian share of the Partitions and these expectations were not a pure paranoia: when the Congress Poland was created, the issue of the lost territories on the East had been raised.
So Nappy is facing a serious dilemma of having a balanced act: the Poles may (or may not) be awarded but such an award should not cause friction with the bigger player, Russia.
I would not overestimate influence of Walewska or any other Polish figure (**): Nappy usually kept the bed and politics separate and held an opinion that he already did enough to reward the Poles who, anyway, did not have an option but to follow him.
But, in practical terms, if Nappy wants to break Prussia he has to cut off either East Prussia or Silesia. Russia is not interested in EP but would be against giving it to the Duchy. Silesia is much more “neutral” in that regard. With Austria - Galicia is another “toxic” issue by pretty much the same reasons except that Russia may want at least a part of it.
(*) If anything, there probably would be a certain amount of unhappiness about getting more Germans: there were already complaints about having too many of them both in the civic and military service. Neither would it provide noticeable opportunities for getting estates there: no free land available. Austrian Galicia was seemingly much more attractive.
(**) Allegedly, after Kosciusko expressed his ideas to Fouche and he communicated them to Napoleon, Napoleon shrugged them off as a complete foolishness.
If Napoleon can appease Russia, he can reward the Poles. While mentioning Walewska was a little joke of mine, I still believe that strong Poland would be a useful French watchdog in Central Europe and potentially the first line of defence against Russia. So e.g. Napoleon can promise the tsar that there will be no French troops in Poland. Poles would be too weak to launch an invasion of Russia on their own and they would be told that France will not back them in any attempt to regain their lost territories.