The issue was taking Moscow. Most of Russia is a wasteland. Once Moscow was stabilized, they could take the oil fields in the Caucuses and not really give a feather or a fig about millions of Russians starving in Siberia. BTW, with Russia prostrate, the Japanese Army in Manchuria could be relied on to over run eastern Russia.
Not realy.
Napoleon DID take Moscow, but was forced to withdraw, simply overstreached forces.
Also, Moscow is not target at present. If Russia is invaded by NATO, the goal would be northern parts of coastland with vast reserves pf natural gas and oil. Problem is they are 2-3,000 kilometers deep inside Russian territory, and for safeguarding that bug chung of land NATO would need 3-400,000 troops at least at all times.
And losess would be pretty high i thing. Average 10,000 per year killed on occupator side.