The thief on the cross died prior to the institution of the NT rebirth. How to experience the rebirth was revealed on the Day of Pentecost when Jesus shed forth the Holy Ghost. (Acts 2:36-42) Jesus prophesied about this when He said, repentance and remission of sin (a reference to water baptism) would be preached in HIS name to ALL nations BEGINNING in Jerusalem. (Luke 24:47)
Those who believe in Jesus, believe all of the word. (John 1:1) According to Jesus, the word is what all will be judged by. (John 12:48) Jesus said He who believes and is baptized shall be saved. (Mark 16:15-16) And Jesus is the author of salvation to all those who obey Him. (Heb. 5:9)
Much of this is wrong. You need to read the Bible more carefully.
For example, you say that the thief on the cross died prior to the institution of the NT rebirth (whatever that means). So when Jesus refers to OT people in heaven, e.g., Abraham, Elijah, and Moses, did they experience the "NT rebirth"? Obviously not.
What is being "shed forth"? Did Jesus molt???
Repentance and remission of sin are
not water baptism. If that was the case, all those baptized by John in the Jordan didn't need a Savior.
John 1:1 describes Jesus as "the Word", i.e., His state prior to becoming human.
John 12:47, "If anyone hears my words but does not keep them, I do not judge that person. For
I did not come to judge the world, but to save the world."
=> The earliest manuscripts and some other ancient witnesses do not have verses Mark 16:9–20 <= Do you believe Mark 16:17-18, "And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues; they will pick up snakes with their hands; and when they drink deadly poison, it will not hurt them at all; they will place their hands on sick people, and they will get well.”
John 3:16-17, "For God so loved the world that he gave his one and only Son, that
whoever believes in him shall not perish but have eternal life.
For God did not send his Son into the world to condemn the world, but to save the world through him."
Ephesians 2:6-9, " And God raised us up with Christ and seated us with him in the heavenly realms in Christ Jesus, in order that in the coming ages he might show the incomparable riches of his grace,
expressed in his kindness to us in Christ Jesus.
For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— not by works, so that no one can boast."
You should get rid of your Old Testament judgmental, harsh thinking and accept the beautiful kindness of God as expressed in the New Testament.