I know of no textual issue with that passage. Do you?
That would be one that would have to be compared with the simple command to repent and believe ... yes.
Can you explain what Peter meant by "not the removal of dirt from the body" >??
I will try, but this will not be official Church teaching on the matter just as a disclaimer.
Here, St. Peter appears to be alluding to the water used in Baptism, as he alluded to the water of the Great Flood previously.
He is saying the water used in Baptism is not used to wash away dirt, rather to wash away Original Sin, and thus, is required for salvation.
Now, I believe a more important point you should address is the point Petrosius made previously, before your discussion with him got side tracked into the dubious nature of Mark 16:9-20, which is, "Where in Scripture does it say that the Scriptures are sufficient for salvation?"
You also said in your reply, "Some of this will have to wait until later", so I would hope that question of Petrosius' will be addressed in a later post of yours.
Regards,