"Is there really no easy way to make things work?" In a word NO!
Would you stay in a relationship with someone who was sill in love with her previous boyfriend? Who would meet with him at least once a week? Who would take your kids to see him and teach them that he is a better father than you? That they should reject what you say if it conflicts with his ideas? Her religion will be the old boyfriend in your marriage and she will not likely ever stop seeing him.