I realize that you may have found all the information that you want. I am from the same Svartti family. I am from Eben Junction, Michigan (originally). This is what I know. The name was indeed changed to Vartti, (Isak). I am acquainted with this family. Another brother, Johan, my great grandfather, changed his name to Maki. My grandfather, Johan, changed his name to Suojanen and when he arrived in the States and it became Swajanen, which is my maiden name. According to my father, Frank died a single man, and is buried in Gladstone or Escanaba, Michigan.
So, that is a brief account for three of the brothers. Interesting info on Jacob. I wonder what happened to him.
Furthermore, I have found descendents of two Maki families (brothers of my grandfather) residing in Pori.
I have not done any research of late. I do find this thread fascinating.