The actual time in the air would be 5.9 hours (probably longer, since spec sheet range numbers usually are at economy settings, but speed is quoted at 75%). Two fuel stops, however, are going to add 1.5 hours (45 minutes per stop, which is conservative) for a total of 7.3 hours.
A normal lens or normal prime is a lens with a focal length about equal to the diagonal size of the film or sensor format, or that reproduces perspective that generally looks natural to a human observer under normal viewing conditions.
The Barlow Lens is an eyepiece. You put it in the telescope in order to look through the telescope and actually see something. It changes the magnification of the telescope. It may be labeled 2x or 3x to indicate the magnification change.