Very jealous of your research trip, Rose. I've never been to Russia and probably won't in the near future. My book is set in Soviet-occupied Germany, so I'm okay on that research-wise. But still, would love to see Petersburg etc. My character is a Leningrad girl, so it'd be relevant...but only in a backstory kind of way.
It sounds like you're nailing your research, but in case you need to dig more into Russian culture from the inside out, I can't recommend the journalist Svetlana Alexievitch highly enough. In case you haven't read her -- She's known for Soviet-centered research (what did it mean to be a Soviet? etc), and she won this year's Nobel Prize for Lit. But reading her nonfiction books all together, especially the one about women Red Army soldiers (my GO TO research for my character), you get a great sense of how regular Russians were feeling and thinking at a deep level when their country went through such profound changes over the 20th century. Her interviews are just so stunning and moving, presented in people's own words. So you also get a good sense of how Russians speak even when reading it in translation. Really helpful for dialogue etc. Again, this might not exactly hit the stuff you need for your books, but to me, Svetlana has hands down the best research out there on everyday Russians, especially women.