man surnamed Kongel
Doesn't ring a bell, a very atypical name. Are you sure you got it right?
she was from a noble family.
Could you give us a timeframe? was it in 1910, 1930 or 1940? She could be from a noble family or not. You're right that many Jews converting to Catholicism took as their surnames the place they came from or a region hence Mazowiecki or Leszczynski could be a name of a Jewish origin.
On the other hand Leszczynski is a well know noble family from a region called wielkopolska that came to prominence in the beginning of the 18th century - briefly. Hard to tell really.
Also it doesn't necessary mean that Leszno has been founded by the Leszczynski family. They could drive the name from the main property they owned. A one thing is certain they are connected to the place and their are an old (ancient Polish noble family).
In more recent centuries, Poland reverted to Catholicism and became very anti-Semitic.
WTF? Poland had been funded on the Catholicism and European Christian culture. That had been a basis that formed Kingdom of Poland and later Commonwealth - a tolerant Polish culture rooted in Catholicism, a branch of western civilization in eastern Europe.
Growing up as an Anglophone you have picked up will nilly Protestant based anti-catholic propaganda and more than few prejudices produced by so called enlightenment age (18th).
By the way define VERY anti-Semitic? That somehow baseless statement is being repeated all over by people who really a VERY vague idea about history and no notion of historical truth.
I personally found VERY anti-Semitics certain circles of Polish-American, some of their views on the Jews expressed freely would have shocked an averaged out of the mill person in Poland. Not to mention views on Jews coming from a Palestinian community.
All in all Some Jews are giving a tit for tat if not more...
I have no way knowing your age. You could be 20 or you could be 60 that would place your ancestor in a different timetable and in different circumstances. You need to give me a date, approximately, and I'll tell you ( approximately) what your gran have been doing in Lithuania.