Yes - I have 82 inches of RO for door currently to the concrete slab. Of course I'll be putting in flooring - carpet. That will take up close to an inch. So I may need to shave a door just a bit. My question is - should I be installing the pre hung doors first - or can I sheet rock then put in the doors after?

The basement ceiling height of the house we lived in when our kids were teenagers wasn't much higher than yours. My husband sprayed the underside of the main level floor matte black, covering all pipes and ducts. If you DIY, be sure to use a good respirator mask. Our son was the same height as your husband (now slightly taller) and my husband was just a tad shorter. Neither one was bothered by feeling as if they were about to bump their heads. We had no issues with dust. As for noise in the basement, I think it was only noticeable when someone overhead wore high heels. I didn't find that the sound of video games or movies in the basement carried upstairs any more than in a later house with a drywall ceiling. My family liked the look and I was happy to put the money that would have been spent on a finished ceiling toward other things in the house.

since this is a powder room and not a main bathroom, and you are restricted by ceiling height. I would do recessed, or i would wall/mirror mount two sconces on either side of the sink. a single pendant light could be ok but would only light one side of the face.

You should contact your building department and ask them if it would be ok. This is the code requirement: R305.1 Minimum height. Habitable space, hallways and portions of basements containing these spaces shall have a ceiling height of not less than 7 feet (2134 mm). Bathrooms, toilet rooms and laundry rooms shall have a ceiling height of not less than 6 feet 8 inches (2032 mm). Exceptions: 1. For rooms with sloped ceilings, the required floor area of the room shall have a ceiling height of not less than 5 feet (1524 mm) and not less than 50 percent of the required floor area shall have a ceiling height of not less than 7 feet (2134 mm). 2. The ceiling height above bathroom and toilet room fixtures shall be such that the fixture is capable of being used for its intended purpose. A shower or tub equipped with a showerhead shall have a ceiling height of not less than 6 feet 8 inches (2032 mm) above an area of not less than 30 inches (762 mm) by 30 inches (762 mm) at the showerhead. 3. Beams, girders, ducts or other obstructions in basements containing habitable space shall be permitted to project to within 6 feet 4 inches (1931 mm) of the finished floor. R305.1.1 Basements. Portions of basements that do not contain habitable space or hallways shall have a ceiling height of not less than 6 feet 8 inches (2032 mm). Exception: At beams, girders, ducts or other obstructions, the ceiling height shall be not less than 6 feet 4 inches (1931 mm) from the finished floor. That said, some jurisdictions in neighborhoods with older homes allow more flexibility when it comes to ceiling heights, so they would be your best bet to go and get the answer. Good luck