The definition of a climax is that it is the point at which there is no turning back: the outcome is fixed. Some say it the most emotional or most exhilarating point. While these aspects may come into play in a climax, they are not, by definition, required. A climax may be a decision, a determination, an epiphany. These may be very quiet, unemotional events and yet be the climax.
Having said this, I second your opinion that the point of no return, the point at which the outcome is determined, is when they are clear of Ember and on the journey. I also agree that the things you enumerate are elements of the falling action. Emerging in the light on the hillside is the resolution--though it is a resolution that allows for the sequel!