I have browsed through all the postings on this thread and still don't see any names. Perhaps you are concerned about privacy. Some of us have special expertise in assisting with certain ethnic groups, certain religions, certain specific areas of interest, and expertise that allows us to see important data that might be missed by some types of searches and by some people not familiar with all the material available. Were your ancestors Jewish, Roman Catholic, Orthodox, German Lutherans, German Baptists, etc.? Even knowing that could help.
You are correct about needing a local reference because Russia is and was a very large country in that time frame, even larger than today. If you post names and dates, you might get more help.
One point I can make is that there may be a migrational connection between Russian Poland and modern day Ukraine, both governed by Russia in your time frame. However, Russian Poland never included any Ukrainian territory. The Polish Lithuanian Kingdom did include parts of Ukraine but that was long before this time frame. Also, the part of modern Ukraine known as Galica was governed by the Austro-Hungarian Empire at that time. It was briefly under Polish rule between the two World Wars.