I don't know whether is it going to help in your research but I thought it would be good if you had correct Lithuanian spellings for all of surnames that you mentioned.
Stanislovas Jurgaitis (Jurgaiciutes means Jurgaitis in plural feminine form)
Julija Grybauskaitė (Grybowska is the Polish spelling, Gribauskas is the Lithuanian masculine form of this surname)
Matas, Motiejus Pašakarnis (this surname is found in Northern Lithuania, however it is spread around, try phone book on 118.lt and play a little with roots of the surnames, no Lithuanian letters needed)
Magdalena, Magdelena Marija Valantaitė, Valentaitė
Juozas Valaitis (Valatis is somewhat mispelled)
Petronėlė Garbenytė, Garbečiūtė (possibly)
Kumbrevičiūtė (can't come up with anything on her name)
Kotryna Alvikaitė (Alvikas is the correct surname for male)
Ambrose could be the second name but not a surname.