I've only found one document listing Katryzna with the maiden name "Sapota", and about 5 listing her as "Fisher" or "Fishorek" so i've ruled out Sapota as being accurate.
The church they were a member of as you said only existed since the early1900's so trying to find records before that won't happen. I've tried without success to try and find the church they would have gone to before that one was built.
Thomas died in 1917... would it have been necessary for him to register as an alien or be naturalized pre 1917? If not, I have strong doubts he would have unfortunately.