1) As I stated, Christ could forgive anyone he chose to forgive. I can not for sure tell you why baptism is required in the New Testament, I just know that the Bible so teaches. In baptism, we are buried and raised to a new life, which parallels what Christ has done for us. It is not the water that does anything, it is our submission to the will of Christ.
2) There is no proof that the thief on the cross had not been baptized by John the Baptist. The Bible clearly states that many in the area were baptized, so he very easily could have been one those who had been baptized. Either way, the fact is Christ had the power to forgive sins while He was here.
Then I don't see the problem here. Clearly, if Christ can forgive whom He wants to forgive on the basis of that person's repentence and decision to trust Him, then baptism isn't "required" by definition.
OTOH, if a person claimed to be saved, but refused baptism, we might wonder if there was a problem, since they were starting out their alleged Christian walk in disobedience.
There is no proof that the thief on the cross had not been baptized by John the Baptist.
There's not a shred of proof that he had, either. And if he had been baptized for repentence, would he still have been called a thief by the authors of the Gospel accounts?
I think that you're overreaching and presuming a lot in order to get around an obvious hole in your theology in this matter. But as long as you believe that it is your trust in Jesus Christ, His diety, and His work on your behalf on the cross that saves you, and not the fact that you've been immersed in water, it's really a relatively minor issue that's not worth getting into an extended debate over.