First question: What the records really say?
How did you figure out from them that ” there must have been a mass execution of Jews on 7 March 1612 in Poznan”.
Aren’t there any other possible causes for sudden death of many? ( fires, accidents, plaques)
I don;t know what the cause was, but for example in 1613 there was a fire that destroyed the Jewish quarter in Poznan.
When you write „in Poland, on very ripe ground for anti-Jewish sentiment”
the words of Moses Isserles ( XVIc Rabbi of Cracow), come to mind:
“If God had not given the Jews Poland as a refuge, Israel's fate would have been unbearable indeed”.
And why the Poland was called at that time “Paradise of the Jews”?
And Chmielnicki’s uprising? – that was a completely different story.
Let's try to seek the truth about the past, instead of building fantasies out of stereotypes.