If I understood the story correctly Ra's was spared the Pit but his wife took his place. Why didn't he break into the Pit to save her?
Ra did not know his family is in the particular pit until the time, his daughter Talia informed him. When he was exiled he thought only he is punished for the love with the daughter of the warlord.
So Ra was unaware of his wife's imprisonment in the pit. So there was no reason for him to come back. But later he found out what happened to his family by Talia after she escaped the pit. But as his wife was dead by then, there was no reason for him to come back except to take revenge from the prisoners for the barbarism they did to his family. This concept is clear from Talia's admittance to Batman.