I guess there are two games being portrayed are different. The first opening is postively amazingly good in the South ( Hats off) , underwhelming in the North, as there will be no pressure on the Sov to Evac Leningrad at all costs ( been there done that). You should be able to relieve the whole Lvov pocket with your lovely Mech forces near his Pz Regiments, but you may lose more in the end vs buying more time if you choose this path. It is not salvaging the Kovel forces that irks me as Sov ( and I have failed in a current game).
Just humbly proferred suggestions:
IMHO the Crimea is the bleeding ulcer that the Peninsula was for Napoleon. Dig in and deny it to the Axis unless she fights for it. Axis players like to get the Donbas, but the mesmerising goal is activating AGA and AGB - exploit it. ( been there been mesmerized, lost the Pz Corps)
Keep 2 or 3 MP 22 Cav always ready every turn, sitting on RR, for moving through the Axis ZOCs to relieve weak pockets. Do not put them on Reserve as you need them to be there for you. Do not be tempted to use them in combat. Creat the ability to do a deliberate attack with 8CV (after moving to the line of departure) of Sov Inf units, all in the same Army, with multiple Air Bombing prep, and 1:1 v 2:1 will mean victory against a single stack Axis Mech div. You might even get a rout if there is no retreat route (hint hint) . Your Tank Divs can only move a short distance before losing the ability to do a deliberate attack. They can go on Reserve as the AI cheats of course, even when working for a human :)
Note: the attackers only have to be in same army at the time of the actual attack - save APs to do this sort of thing and move your HQs next to the battle.
All your air units must be on rail lines or trucks go poof. Actually, anything not explicitly needed to be in a non-rail line should always be on one.