There were 295 SIDORs that passed thru Ellis Island port to America. None of them have that they are Romanian. The Slovak phone site is at www.zoznamst.skand you already know that the name exists there.
The Romanian phone site at http://www.whitepages.rohttp://www.whitepages.ro and the name SIDOR lists in the town of BISTRITA's phone book.
There are names that are Christian and Jewish. Have you checked the LDS-Mormons-Family History Library if they have any church films for Bistrita from which you can gather ancestral information.