That is a exciting news for sure. So close and yet still questions but genealogy is never ending.
So than the KOCHNOWICZs arriving NY EI somehow are related or at least provide you with a location of Petrus's mother.
Kochnowicz, Efin Bobrik, Russia 26 1884 1910
Kochnowitz, Fjodor Bobrik, Russia 23 1889 1912
Kochnowitz, Petro Bobrik 30 1875 1905
Your Catherine could have come under her maiden name or her sister's first name. She might not have wanted a paid ticket to go to waste. Could Catherine come thru Canada to America?
Petrus's surname is not an easy one to pronounce. The closes in spelling in Poland I find
Szamryło.
We never looked into Ivan's location where it might be in connection to Konotop and Bobrik.
Szemrylo, Ivan Podberezie, Russia 36 1875 1911