One possible storyline could be Jack's journey of self - discovery and healing. He might start to confront his past abuse through the help of Mary Poppins' magic and the support of his friends in the story. As he delves into his memories, he could gradually learn to forgive himself and those who wronged him in the past.
A story could also focus on how Jack's past abuse affects his perception of his own worth. He might think he doesn't deserve good things. Mary Poppins, being the magical nanny she is, shows him all the wonderful things he has accomplished and the potential he has. She helps him see that his past does not define him, and he can create a better future for himself.
Perhaps a storyline where Jack's past abuse has made him distrustful of certain situations or people in the new story. For example, he may be hesitant to form close relationships. Mary Poppins then uses her unique ways to show him that not all relationships are like the ones from his past, and he slowly starts to open up. In the end, he overcomes his fear and builds healthy relationships.