Let's try to have glfw manage as much state as we can. It's a pain keeping your state synchronized with the APIs internal state and in my experience leads to a decent amount of annoying bugs.

For full screen we can use:
http://www.glfw.org/docs/3.0/group__window.html#gaeac25e64789974ccbe0811766bd91a16

For width/height we can use:
http://www.glfw.org/docs/3.0/group__window.html#gaeea7cbc03373a41fb51cfbf9f2a5d4c6

For openWindow we can MAYBE use glfwWindowShouldClose() but look into it a bit more:
http://www.glfw.org/docs/3.0/group__window.html#ga24e02fbfefbb81fc45320989f8140ab5