I see a stark contrast between being sold to slavery with the whole family and being made repay a debt, after which there is freedom. I know that in the context of the teaching of Christ about kingdom of Heaven, everlasting life, and forgiveness of sin, the parable has a soteriological meaning, rather than a plain ethical meaning that is on the surface. These elements are sufficient to conclude that those who are forgiven yet burdened with sin work it off outside of their free will (in jail), and therefore after their death. The parable effectively describes the Purgatory, it is the natural reading of the parable.
Your exegesis is defective because it does not take into account the difference between the eternal punishment and temporal one, that is so prominent in the text, and makes God first granting, then revoking his mercy. As to the size of the temporal punishment, no one is arguing that Purgatory is short or easy, only that it is finite. It is you who starts with the assumption that Purgatory cannot be in the Scripture because Luther said so, then proceeds to explain the parable away contortedly.
I'll be back tomorrow.
The man owed ten thousand talents. Each talent was worth about 6,000 denarii, or 6,000 average days' wages. Grand total: 60,000,000 days' wages. If we figure an 8 hour day at $10/hr, that's the equivalent of 4.8 BILLION dollars.
How exactly was he going to ever pay that amount off? Especially while being tortured in prison?
That's the soteriological lesson: We owe a debt that we can never pay, before or after the King calls it due. Therefore, He in His grace ate the cost, and freed us of our debt--but He expects those of us who owe Him so much to be equally generous to those who owe us so little. "Forgive us our tresspasses, as we forgive those who tresspass against us."
Ergo, it is not my exegesis--based on the words of the text and their cultural, textual, and theological context--that is flawed, but your eisegesis--based on an unBiblical Roman Catholic tradition--that is.