Once Germany turns its luftwaffe back to the west Russia gains ground back quickly. Russia withdraws to the Urals often times without a fight, preserving her army for the fight later. Yes, Turkey is usually triggered. The Istanbul objective becomes a forted down stronghold until the end.
Western Allies have obviously taken Africa and forced Italy to submit. They usually land in France a little early, as soon as air superiority is gained. Germans have elected to turn the entire luftwaffe against the Western allies in order to delay said landings as long as possible. This spares the russian factories and keeps the red army pumping out tanks, which they will need to move fast enough to race to Poland, Berlin and the Balkan objectives.
Keep in mind if Germany is making this hard of a push deep into russia, very little can be spent on other fronts, so the allies are not troubled.