If you see anything like plastic or paper, under which would be the drywall, then you have a vapor barrier. If, as you say, you can see the back of the drywall from the attic, then you DON'T have a vapor barrier.
When you install Kraft-sided Insulation (w/the Kraft-side facing the living space), it needs to be tucked a little under the joist. Simply laying it in may be OK but it won't have the 'seal' you're looking for. That's why when you look at this type of insulation, you'll see 'ears' on the Kraft Paper that allow the Installer to staple it to the joists (or studs when doing walls.) You'll need long clothes, a mask, and gloves. Do it when it's COOL outside!!! Yes, Kraft-side on the BOTTOM (facing the living space.)
Yes, it's possible to add Facia Vents (vs. Soffit Vents.) I've learned this recently. YOu need to visit possibly a Siding Supplier or Roofing Supply House. (Look in the YELLOW PAGES for either or both.) The Supplier will tell you the BEST and 2nd Best way to do an install.
RE: The power vent, consider adding a thermostat in the electrical line. Have it come on at, say, 105 degrees or something. You really only want to use it when Mother Nature doesn't do the job well. I see them working against you and the house. They may not be properly sized. You particular vent may be working very hard (hence, it draws warm moist air from the house into the attic.) Then, on the other hand, it may be undersized and NOT doing the job. It's hard to say w/o having the Power Vent speced-out along w/the Gable Vents.
For now, my best to ya and hope this helps.
Jay J -Moderator
PS: Your call - You may still need to get rid of ALL the existing insulation in order to have the new insulation installed. As I see it (sight-unseen), that's the best way to go. Talk to a Contractor about doing the removal yourself. YOu may save some $$$. Just be sure he tells you how to 'bag' it and anything else ...