1.). Your Polish forbear need not apologize; he's Polish, and, thus, an uninvolved party.
I don't know why white people always collapse with fear at the idea of having to apologize for the Trans-Atlantic Slave Trade(TAST); subsequently, they say silly things like this.
"OMG, maybe EVERYBODY might hafta apologize for slavery!"
No. No, they won't.
I hear this argument a lot, HR.
2.) I have some familiarity with Medieval Poland, but @BetterJudgment is the Tenured Medieval History Professor, and I'll be goddamned if I'm going to usurp his position.
Maybe you could pay for me to go to Uni and get a Ph.D. in medieval European history, though. Perhaps you could all pitch in; this appears to be a forum chock-full of Rich White People.
I think Poland had serfs. I think that; it may not be true.