The records in Lithuania from the time frame you would be interested in are recorded in church records so you would need to know where they were baptized.
I'd suggest finding the church where they were married in the U.S. and get a copy of the church marriage register entry for them (likely in Latin) which may list their place of baptism as well as more authentic surname spellings. Don't settle for someone providing you an exceprt/transcription.
The reference to Vilnius is likely to the Russian province (called gubernia in Russian)rather than to the actual city itself.
The entry you found for Petrona uses a Polish spelling for the surname based on the use of the "W" rather than "V" in the Lithuanian spelling.
The SKI ending for Simon's surname is a Polish spelling and vey well could Vasilauskas (also Vasiliauskas).