It didn't make sense that Jack was telling him to get away from Valtrar. It actually never made sense that he became a softie. Stephan thought he would be more inclined in killing him under any excuse. Furthermore, wouldn't it be better to take him back to Valtrar under the excuse that he was Maddock's son? They could use him. They could try to fill him with lies to use him, like how everyone did. It would be easy, they would say. Since Stephan was still young, he could be made into whatever they want. They would have someone potentially strong under them.
"Isn't it better to take me to Valtrar rather than recommend me to stay away?"