From: Seattle, WA
My reccomendation is to trade space for time and slowly build a strong strategic reserve over Winter. Not an handful of divisions, possibly an entire front. Let him overextend himself for the next (few?) turns. Yes, deal with the frontline crisis, but make sure that *every turn* you build a couple of infantry division for your reserve and assign good leaders to it. I bet you will be tempted to commit those units piecemeal, but don't. Decide what cities you can afford to lose and stick to those decisions, even if it is painful. Make sure you have cheap support units (sappers are always good, I did tests with AT guns but they do not seem to be worth much, artyllery if you can afford it) attached to your Armies.
Do not worry much about Corps, they are expensive and ..well have they worked for you so far? Stick to simple and cheap. Also, morale is important, but only counterattack when a really good opportunity presents itself, not because 'you have to'.
I probably sound like your financial investor, but playing the Red Army requires patience and small steps. Let the Whermacht take chances and overextend itself, your time will hopefully come.