Dont be pedandic.
Most of the former Russian states would have many groups of people who consider themselves as of Russian background, ergo the potential for Russia to consider these people as Russian.
I do feel, on the whole, Russia is likely to be comfortable with the EU. However when their former states chose the EU over Russia, then of course this is going to make them nervous.
Their entire Black Sea base is in the Crimea so they would feel vulnerable in many ways in the advent of Pro-EU politics.
Not condoning their behaviour. Far from it. In fact 100 years since the start of the first world war we still have coutries concerned about the growth of their neighbours and the potential impact this could have on their own economy, growth, political influence, colonialism (historical ties) and military might.