> Just found out that the name of the city was actually Trubowszczyzna, it
was an osada (?) in the Kozłowszczyzna > gmina, this place: http://www.radzima.net/eng/miejsce_answer/trubowszczyzna.html?id_comm=7760
> does this change anything?

Did he live in this place between 1921-1939 or prior to 1921? In any case, this a completely different region that was in western Belarus near Slonim. Not in north-eastern Poland. It’d be easier if you used Belarusian or Russian names for places instead of Polish in Belarus.