Why are we scared of the Russians again?
"Moscow uses the cash to sustain the only military-industrial complex which can give the Western one a fight, meaning that the West must keep spending money on staying ahead."
So? Putin's Russia may not be a land of milk, honey, democracy and a genuine free market, but it's not the Soviet Union anymore, even if its air force still has red stars on its planes. The Soviets were a threat because up until Gorbachev just enough of their leaders still believed their own propaganda or at least felt they had to pay lip-service to it.
Putin's Russia doesn't have that sort of ideological baggage. Yes they want to be left alone to run their "managed democracy" as they see fit without Western interference, and yes they're grinding the heel on the Checens, but that's because rightly or wrongly they see Checnya as part of their territory.
If Putin really did want to restart the USSR, he could have absorbed Belarus in a moment any time in the last eight years - but he hasn't, much to Lukashenko's disappointment. And as for the idea that the Russians might want to head west again - why on earth would they when - as you say - we're such excellent customers for their oil and gas. It seems to me that the more we buy Russian gas the safer we are from them as they're hardly going to threaten their best markets.