70% of Russians live in the European side of Russia. Not all of them are White Christian Russians. There are plenty of working migrants from the less prosperous parts of Russia. Don't oversimplify Russia.
If Russia was supposedly so close to Christian Europe. Why then did Christian Europe treat it so horrifically? The Russians have good memory. They remembered the Napoleonic Wars, the Crimean War, WW1, Russian Civil War, WW2, Cold War, bombardment of Yugoslavia, etc. All done by Christian Western civilisations. Even when Russia was the Russian Empire.
Russians especially remembered how lowly they were regarded by the Germans and their European friends in WW2. The Siege of Leningrad was one of those nasty highlights. The Chinese didn't do that. It was Christian Europeans who did that.
I see Russia and China working very well in Central Asia. Russia takes care of the security, China brings in the economic development. Nothing like the outright zero-sum aggression that the West is inflicting onto Russian influence in Eastern Europe, Middle East, North Africa, the Caucasus, and the Balkans. Hell, the West still has dreams of color revolutions in Russia, and breaking Russia up.
You say that China and Russia are on and off friends. And they only got closer these last 20 years. You speculate that they'll be friends only for today, and then become enemies tomorrow. Why? Jealousy? Its a lousy argument. In the last 20 years, every major Sino - Russo friction points from territorial disputes, to commercial disputes has been discussed and settled. Try comparing that to how the Christian West treated Russia during these last 20 years. Howabout the last 100 years? Russians are not morons. You're gonna need much more than European ethnicity, and Christianity to gain their trust.