My understanding is that God will forgive whom he wants to forgive, but of us, it is required to forgive 7 X 70. This equation is symbolic to mean that we may need to forgive every time we think of the injustice that has befallen us (or the victim). I used to feel the same way. I used to ask my attorney father, "Where is JUSTICE when a criminal walks free!?" I would also ask him all of these same questions you ask above. His response was that without Mercy, there is no Justice. The two need to go together in order for each to work correctly.  Throughout my life I have learned that those who offend, and we all do at some point, don't walk away unhurt. The offender is hurt, too, although we may not see it. They have to live with the consequences of their actions; whereas, through forgiveness, the victim can heal and move on. In the end, I give it up so the offender won't have control over me and I hope Karma/God/the Universe, whoever, takes care of the offender with both Justice and Mercy so that both of them can be paid in full.

Post #3 raises a good point. Failure to forgive hurts the person who does not forgive. The act of forgiving is very difficult and requires that we allow our base nature to change from something human and corrupt to something closer to the model that Jesus provided.

I can see how you would interpret forgiveness for a crime as an insult to the victim, but I think the point is that the victim also has to find some kind of forgiveness.   The forgiveness is not really going to help the perpetrator.  However, lack of forgiveness will lead to hate and bitterness on the part of the victim.  Forgiving the perpetrator may be the only way for the victim to move on.  In this way, I think Jesus is being a good role model.

I disagree with your premise.  Christian teaching does not tell us that Jesus forgives sins "for free."  Instead, people actually have to repent and change in order to be forgiven.  It is of course hard for a victim to handle this, but that is part of what makes us human and not divine.

There is, maybe, a tension between forgiveness of sin and obtaining justice for crimes. I think the most common way to resolve this tension would be to say that forgiveness does not necessarily mean that one should not be held accountable for their crimes. People can still be prosecuted under law whether or not their victims, or their families, forgive the accused.