Having been in the same position, Jack knows when to stop pushing and let the words he's already said be given consideration, like North had done for him. And while Jack is under no illusions that the scope of his advice will ever come close to that of the Guardian of Wonder, his intention here isn't to give Booker some kind of grand revelation about his life. He'd offered a place to stay and that was not going to come with any kind of lecture.

(He didn't have to guess which "her" was being referred to. And Jack did intend to press into the details of that at a later date, just in case... much later.)

Instead he leaned forward and pulled some crackers off the plate, a silent reassurance that he was not looking for an argument here.