Certainly Russia would benefit in a number of ways, as you have articulated, by a warmer climate. The city of Murmansk for example, far to the north, has benefitted greatly in recent years by warmer tempertures. But you left out some important climate related problems.

Rising sea levels, especially if the West Antarctic ice shelf broke off and melted, would severely flood coastal cities like St. Petersburg, Vladivostok, Murmansk, and much of Russia's coastlines. Droughts to the south of Russia would cause mass migrations north causing social and political chaos. And of course climate wars around the planet and the instability they cause would not make Russia, or anywhere, a safer place.