Kushnevich sounds familiar to me. Andrzej Kuśniewicz (different in writing but the same in spelling), outstanding Polish writer, poet & novelist born in 1904 in Galicja... most of his writings refers to that region. One of my favourites Lekcja martwego języka (Lesson of a Dead Language) takes place in the hometown of my mother's family - Turka nad Stryjem. He died in 1993.
I know nothing however about his Jewish origin. I know that he survived IIWW in France fighting in Franch resistance movement...