Dreams often serve as reflections of our subconscious thoughts, feelings, and experiences. Your dream appears to weave together themes of adventure, concern for your son, and the presence of notable figures from the comic book world.

1. Comic Book Day and Characters: The setting of a comic book day at the library highlights a space of creativity, knowledge, and fun. Characters like Stan Lee and Chadwick Boseman may symbolize inspiration and the importance of storytelling in your life. Their presence suggests a desire for connection to creativity, perhaps indicating that you seek to inspire or encourage your son in imaginative pursuits.
2. Concern for Your Son: The recurring theme of searching for your son suggests a deep-seated worry about his safety and well-being. Dreaming of him running off and getting into trouble could reflect your parental instincts and the anxiety that comes with raising a child, particularly in a world filled with distractions and dangers.
3. The Santa Sack and Rescue: The Santa Sack display filled with water and the struggle to rescue your son and other children signifies a sense of urgency and responsibility. It might indicate your fears about being unable to protect your loved ones from unforeseen circumstances. The act of performing chest compressions and saving him symbolizes your determination and resourcefulness in crisis situations.
4. The Elevator and Adventure: The dangerous elevator and the subsequent adventure represent transitions in life. Elevators can symbolize ascension or descension, indicating changes in your life or your son’s growth. The idea of him running into another elevator may suggest your concern about him being drawn into new experiences or environments without your guidance.

Overall, your dream reflects a blend of creativity, parental concerns, and the challenges of navigating life's unpredictability. It might be beneficial to take some time to explore your feelings regarding your son's independence and your role in supporting his growth while ensuring his safety. Emphasizing open communication and trust may help ease some of the worries represented in your dream.