To answer your main question directly. Expect deep meaning in everything Jesus said, but not necessarily the meaning that you expect. You can also expect entertainment value.
To answer your other questions directly, Jesus recognized that monarchy, torture, and debtor’s prison’s existed. Recognition of reality is not necessarily approval. He used their reality to convey his message to those around him. He expected people who were serious about understanding his meaning to be smart enough to adapt these ideas to power structures of their own time.
Everything in this lesson can be applied easily to your own life today despite the fact it was put in terms of a king, torture, or debtor’s prison. Imagine getting caught by your parents, your boss, or the police doing something wrong and being given a second chance. Then, instead of treating someone else the same as you were treated, you use your power over them to punish them to the full extent of your power. When those with power over you find out about this, what would you expect them to do?
As an aside, we should realize that, from a historical, scientific perspective, all of those institutions—monarchy, torture, and debtor’s prison’s—have been around a lot longer than our current replacements. To you, they may seem obviously "morally wrong", but on what basis? The morality you use today was unknown before Christ.
Another interesting question is whether today's institutions are as sustainable as those of Christ's time. For all we know, our replacements may not stand the test of time like these older, less kind, less “Christian” institutions have. The only hope for today's institutions have for survival is that people keep faith with the idea of "moral superiority" of those idea that goes back to the teaching of Jesus.