Retorquing the head won't buy you anything.

In fact, I'd bet that the oil that you see around the head bolt remains from the leaking valve cover. They can be a PITA to seal completely and the proper torque on the nuts is critical.

If you are getting an extraordinary amount of oil in the air cleaner and blowby is high, the chances are good that the bottom end is marginal and the oil is passing to the engine via the breather.

As mentioned, it's also likely, on high mileage engines, that the turbo seals leak some oil as well.

The combination of high blowby and leaking turbo seals will result in some serious consumption.

This one has very little blowby but is consuming a quart every 1500 miles...........most likely due to the turbo seals.