Nope, still doesn't work -- He was under the OT regardless if Jesus died 1rst.
Jesus might have died first, but they knew nothing of
Matthew 28:19.
That command was not yet given. Even so, I would say that it only works after the resurrection. In which, the thief had died before then. Obviously it couldn't have taken affect because he hadn't risen, it would be as though he was still "in the water," as a figure of speech. Buried.
The last part of his purpose ( resurrection ) had not happened yet.
Repentance = Death
Baptism = Burial
Holy Spirit = Resurrection
Comprehend it now?
Aside comment: It WAS easier to go to heaven in the OT than it is now ( NT ).
Now in the NT, if you LUST after a woman it's the same as "doing it."
However, times were harder in the OT, than the NT.
If you really wish for me to address the whole "faith" situation, I can.