The thing is, he wasn’t nailed to the cross because he had accepted Christ. He was going to suffer on the cross regardless of how he determined his eternal fate, and this had been determined before he ever met Christ.
Really, I can’t see this as penance.
I believe that a man can repent at the very last second of his life; however unlikely it is that he will do so. I don’t believe in punishment for those sins that are forgiven, although on Earth there can definitely be consequences that can’t be avoided.
What I do believe in is that there are rewards in heaven based on your faith and works based on that faith here on Earth. What are they? Don’t know.
Penance is a condition of the heart.
One can do acts of penance, just as they can commit acts of jealousy or acts of passion. It is not suffering, other than the suffering one feels when acknowledging his own sinfulness.
I think many people seem to think penance is merely making recompense to those one has harmed.
Here is one Catholic definition (sorry if stating Catholic doctrine out loud disturbs you as it has obviously done to some others);
1. Spiritual change that enables a sinner to turn away from sin. 2. The virtue that enables human beings to acknowledge their sins with true contrition and a firm purpose of amendment. (See Penance, Virtue of.) Confidence in God's mercy and forgiveness is fundamental to the Christian virtue of penance, along with a determination to be conformed to the passion, death, and resurrection of Christ through the practice of mortification.
True. It was only because he asked forgiveness that he gained his entrance into paradise. As you say, he would have suffered either way. But his suffering ended once he died.
What I do believe in is that there are rewards in heaven based on your faith and works based on that faith here on Earth.
True again. Jesus, himself, said this in Matthew 16:27 and this was also said in Revelation 20:11-13. But, good works alone are not enough. As you say, the good works must be done in faithful service of the Lord to accomplish His goals.