Thank you for that! So it appears to be a big population of Charkiewicz/Harkiewicz on the Poland/Belarus border. So that might explain the references in different census that they are Russian, then Polish and back again. As I imagine there have bee many issues about borders and that being so close to the border it would be an area of dispute?
Do you know where Supockin, Russia is? Is it around that area you've highlighted but across the border? That is where he says he was born - on the immigration documents.