Complex sentence: Mo gives Meggie a pen to write her own ending, and using her arm, Meggie manages to send all the book characters back to their own stories, and at Fenoglio's request, sends him into the Inkheart world as well.
Split into simpler sentences: Mo gives Meggie a pen to write her own ending, and using her arm, Meggie manages to send all the book characters back to their own stories. At Fenoglio's request free him, Meggie sends him into the Inkheart world as well.