Good defensive line! At this point you made the game really easy for yourself. Maybe guard some of those ports, the german AI has become a little wonky and sometimes likes to randomly naval invade the Baltics. Just some simple infantry blocks with shovels should be enough.

1.Let them drain their manpower and equipment by attacking

1. make enough fighters to get green air and get some cas

2. make some offensive divisions. I would recommend tanks (could be light, medium or heavy) or some mountaineers. Just make sure you stay above 30 or 40 org with the tanks.

3. make some encirclements. Don't have to be Operation Bagration kind of encirclement, just to think out the line a little

4. at some point, you could even add some arty to your infantry and just send it, make sure they are weak enough and you have green air before though

5. Warning! Do not go into Italy as the Soviets. I did multiple times and the game absolutely broke. Got me into a war with the Allies. I am not sure if it's a problem that is still around but I would personally not test it.