Significance of Lord Ram breaking Lord Shiva's bow

Pinaka or Shiv Dhanush was the bow of the Hindu god Shiva.
Vishvakarma crafted two divine bows. He gave Sharanga to lord Vishnu and Pinaka to lord Shiva, who killed the demon Tripurasura with it.
The Pinaka bow was given by Lord Parshuram to King Janak to keep it safe while he is performing penance in the forest. One day, Devi Sita in her childhood, while playing with her sisters unknowingly moved the table on which the Dhanush was kept. No one was able to move the Dhanush or the table that easily. Hence Janak decided to keep a Swayamvar and whoever lifts the Dhanush would be considered worthy of marrying her daughter. There are some tales where it was Lord Parshuram himself who suggested this to King Janak.
Coming to the swayamvar, the bow was eventually broken by Lord Ram when he attempted to string the bow, thereby winning the princess's hand in marriage. It is debatable whether he did it knowingly or not. As per the Ramayan TV serials, Lord Ram later explains that even though he did not mean to break the Shiv Dhanush the event of breaking holds several meanings. It was also explained in the TV serial, 'Siya Ke Ram' aired on StarPlus. I liked that version of Swayamvar and the explanation was really amazing. You can watch it on Hotstar.
Lord Ram breaking Shiv Dhanush
He didn't break Shiv Dhanush for insulting Shiva, in fact, he took the blessings of Lord Shiva before lifting the bow. Without Lord Shiva's blessings, no one could have lifted his Pinaka bow. These are some of the reasons which provide reasonable explanations behind breaking the Shiv Dhanush.
1)Lakshmi can only be stationary near Vishnu. So Sita can only be of Ram. The purpose of the Shiv Dhanush had been served. That of uniting Lord Ram and Devi Sita. No one else in this world except Lord Vishnu and Lord Shiva could lift the bow hence it was bound to be broken.
2)Shiv Dhanush was broken to break the egos of arrogant Kshatriyas in that era. For them, lifting the bow was a remarkable feat to show their strengths to others and tell them how powerful they were. When none of them could even move it and a young prince broke the bow in half, they were really ashamed of their actions.
3)Breaking of Dhanush had depicted that ParshuRam's tenure is over and now the earth is in the hand of Shri Ram.
4)Both superpowers Shiva and Vishnu are the same and there is no difference in them.
5)Ravan was informed that a more powerful person than him has come on this earth because he was also present on that swayamvar and couldn't even lift it and was embarrassed when others laughed at him struggling to lift the bow. He left the palace before Lord Ram broke the Dhanush but must have heard the tells of this event.