The child Andrew (Andrzej) did he have social security numbers? http://ssdi.rootsweb.com
Was he naturalized citizen? Did he marry ? If yes, I would think that his CHURCH marriage certificate would have his parents names and where born.
They could have come thru Baltimore, Boston or Philadelphia unless you know that they came thru EI. Have you tried finding them with www.jewishgen.org/databases/EIDB/ellis.html
Search for speling SZPAK, SZPOK.
in 1990 census of names there were 50 STOPKOWICZs in Poland. If we would to do the research based on that information, the most is found in Ks -Krosnienskie woj. I know that is not a precise way to go with the research but when you have no village that might not be a wrong way to go. Surname SZPAK list in Lubulskie woj. of Poland's phone book. SZPAK and STOPKOWICZ list in Podkarpackie woj.