Genealogy / The Name "Kasis" [7]

If ethnically lithuanian, I would say Kazys (or latvian Kazis).But in your case, could be americanized version of his hebrew name.

Genealogy / Szamovo or Szumowo? I Can't Tell Where He Was - maybe in Poland? [10]

My 2 cents :
1.Why his first name is not jewish?
2.Jews in Russian Empire could not buy any land so they could live only in towns.
3. Was he practising any religion?Was his children christened?
4. There is Dna testing nowadays, so you can confirm 'jewisness' (23&me and ftdna to name a few). You could test only his ydna through your male relatives (genealogy.about.com/od/dna_genetics/p/y_dna.htm).