Hi, teccjmom. I'll try to answer a couple of them for you. On the wallpaper stripper solution, 1 cup of water to 1 gallon of vinegar is about right. For the borders, the prepasted works fine--at least it has for us. When you put it up, just put it on with a large plastic sweep and/or wallpaper brush. A lot of people use rollers, including seam rollers, and I have found that they don't do much other than push all the glue out from under the paper.
The furnace question is out of my area, but I think that you will always have problems with acoustic tile in a bathroom. Some others might answer your specific question but I sure think that I would go with some kind of hard surface for the ceiling--plaster or drywall. Even a suspended acoustic tile ceiling would be better as you could just replace the tiles every couple of years. The humidity in the bathroom will always give you problems.