Hi Kristen, I met on internet a brazilian guy (Bruno Juśków Jakubowski) who found his Jakubowski family branch in Dębsk and Szydłowo, two tiny cities few kilometers from Mława, in Poland, that was mentioned here already.

I know the information I'm giving here and now might only introduce an unnecessary confusion, so... if you haven't already found more consistent infos on your own I'll be glad to have more details from Bruno once I'll have met him in Poland the June to come and pass those infos onto you. He'll be visiting his parents in Mława and Dębsk... they're a little bit scattered around the area now after all those long years.