My anecdotal understanding from reading parish records and histories and talking to people is that most were like him - from present day Slovakia and Zakarpatska oblast. Few Galicians. I don't have hard data on this however.
You need to get in touch with John Schweich. He has over 700 parish history books from Carpatho Rusyn parishes and can probably help you a lot. He was featured in the most recent Byzantine Catholic newspaper. I think he has both Catholic and Orthodox histories.
Yes, it depends how much research you want to do.
In general they were from the Rusyn and Galician lands. I expect they were spread out across those lands. If you made a map you would end up scattering dots across those lands in what would look to you like a random pattern.
My choir director's background was Carparthian Lemko from what is now Poland, and I had one friend whose family were Ukrainian Catholic and converted many decades ago in the US. Fr. Obushkevich was a priest who I perceive to be Galician and he was a leader in the Russian Brotherhood, but his parish chose to be Ukrainian Catholic. Yet he converted to Orthodoxy around the era of Alexis Toth, as did many others. I have another friend who as far as I know were already Orthodox but immigrated at that time period from Khmelnitsky region in Ukraine.
It would be very time consuming, if not impractical, to go across the US and map even half of the villages because there were very many of them. I have seen one such modern map of all Rusyn villages from that time period, and there could be hundreds, especially across Ukraine, Poland, and Slovakia, but a few in Hungary and Romania.