[Marcello]

"Even with the Pen that tank stll drove away."

From the accounts of the accidents it seems that tank was evacuated and recovered later (and it was looted in the meantime).It did not drive away from the scene, although maybe it could have done it and it was decided not to do so for safety reasons.
Without special ballistic skirt the side hull, with the exception of the area around the driver which is protected by fuel cells, is not better protected than on the majority of the tanks.A plate of RHA in the 8cm range + side skirts is a pretty common arrangement.From the calculations I have seen and the opinions of some tankers I have read it might not be enough to stop a plain vanilla RPG-7 if it hits head on.Neverthless that sort of calculations require detailed informations on the specific warhead configuration and some additional knowledge I do not possess.