I also thin you underestimate the power of attacking on 3 vs defending on 2. The tanks slaughter the men.

The problem is that UK and USA dont have enough time to do theyr job. If russia stacks everything in bellorussia germany win on 4 turns, if they stack in Moscov germany wins on 5 turns.

Germany spend 12 first IPC`s on 1 tank, 1 artillery and 1 man and places them near the russion border.
Germany buys 8 tanks first round and takes east poland, non combat gerany places everything as close to belorussa as they can.
All your planes are attacking east-poland and land in bessarabia or poland. You take some ships with your subs, but really dont give a shit about the water, let UK and USA take it.
In non if you managed to take the UK transporter in easterd mediteranian, you empty south europe, moving every unit against russia. You also move all men in russia towards russia ( make sure you have enough defence so that UK/USA can invade you on the first round, but 4-5 men + the tanks you keep buying are enough the 3-4 first round ).

If russia stack all forces in belorussa you attack the second round and should win that fight without a problem. Russia then have around 28 units, moslty men there. You can attack with over 25 units, including mainly tanks and fighters, and will have 2-3 tanks left if it goes REALLY bad.
You keep buying tanks and move them + men from southern europe against russia. Next round russia will either counter the tanks in belorussia or move every unit they got into moscov.

Germany keep waving moscov with everything they got and it should fall either the third of fourth german round. UK will not have time to transport units to assist Russia, and they are still no real threat to Germany capitol.

Me and my brother will try to work together with the allies tomorrow, him also beeing Germany, to see if it is possible to stop even when we know what germany is going to do.