From a Biblical Rationalist perspective, the laws of physics are mathematical and empirical principles which never hold exactly or universally in any observed natural system. Laws (a set of statements to which all events conform) may exist in formal logical systems like mathematical models, but we don't have an empirical reason to believe that laws of physics have any real existence beyond their use by human minds to understand physical phenomena. In fact, observation of natural physical phenomena continuously informs revisal of these models by revealing their shortfalls. The laws of nature are a tool of science to predict future or past states within idealized systems that model observable phenomenon, and that is where their power ends.
Often, the english word miracle is used in translation of the Greek word dunamis, which is more generally understood to mean power. A common American English definition of miracle characterizes a miracle as "an event that violates the laws of nature, especially with divine origin." Use of common definitions of American English words to understand Scriptural concepts like miracles makes asking and answering questions difficult. In this case, the definition relies on so-called laws of nature, and so misapplication of the common definition suggests that God created a set of laws that he then breaks at will. This is not the Scriptural position, so the answer to all three questions is a vacuous no, because they aren't admissible.
A Christian understanding of miracles relies on a Scriptural interpretation of dunamis. The words is used to describe acts of God or acts of humans empowered and inspired by his Spirit that transcend ordinary human experience, ability, or understanding.
Do Christians believe the laws of physics were obeyed, and that our understanding of them is merely insufficient to understand what happened?
The Scriptures do not ascribe to creation the ability to operate independently from the Creator. On the contrary, the Scriptures teach that God both set nature into motion and continuously sustains it. The Scriptures say that He holds all things together. The Apostle John wrote that it was through the Word who took on flesh, Massiah, that all things were created. Since there is no biblical foundation for a set of principles which govern the cosmos apart from God, the answer is "no." Christians do not believe that God obeys set of governing physical principles. They believe that God has the freedom and ability to effect his will without regard to human understanding of physical phenomena.
Do Christians believe God does not break the laws of physics, but he changed the laws of physics temporarily such that those laws permitted certain miracles to occur?
As principles of human thought, the laws of physics are not a binding code that God "follows," "bends," or "breaks." The laws of physics exist in the mind, on paper, and in silicon, but the whole of creation is subject to the will of the Creator, and he shows his favor to mankind by displaying his power to them for their benefit, so that they might believe that he exists and know that he is who he claims to be. The answer to this question is "no," Christians do not believe that God temporarily changes a set of physical laws to avoid breaking them when doing miracles.
Do Christians believe God is not only able, but is willing, to break the laws of physics that he created?
This question admits the false assumption that God created a set of independent and universal laws of nature. Scientifically, universal laws of nature represent an era of Newtonian thinking that claimed the orbits of the stars are fixed perfectly and permanently in their place, and the cosmos are a perfect example of divine clockwork. Empirical human thought has progressed beyond a paradigm of static and universal physical principles, and Christians do not need to seek empirical evidence to bolster faith, indeed "Blessed is the one who hasn't seen, and yet still believes."
Christians do believe that God is omnipotent, and is therefore able to effect his will in any mode that pleases him. It pleases him greatly when he doesn't need miracles to convince us, and the Prophets rebuked requests of miracles to motivate faith. The answer to this question is also "no." Christians do not believe that God is able to violate the laws of physics, because they do not believe he is subject to violation of a set of governing physical principles.