Road,
Looking at your pictures it looks like you have the right idea. Its a pretty cool project. One thing I would like to point out though, on the 1st picture of your third post you have ducting going under the floor joists, this is okay, but the way you did it is a little concerning. You are not leaving enough wood for support on those floor joists due to the size of the cut you put into them for the duct. The joists will break on that spot under any reasonable load. The right way to do it would be to frame around the ducting in a "H" to keep the load spread a crossed the floor joists.
I am also in total agreement about the proper R values on your insulation, and keeping the house breathing. Heat, moisture and humidity are HUGE factors on keeping your home healthy. The home breaths through the attic, so as stated above make extra sure your house is properly vented. You might want to look into spray foam kits. They are reasonably cheap, and very easy to apply, or you could do a 1-2 inch layer of spray foam, and a layer of the fiberglass. Just make sure under that, that you have the pink or green foam breathing ducts for the roof. That way you will get a great R value, and still allow your roof to breath.
If you can, to deal with the heat, a vent-able skylight set, or low E Glass windows would work pretty well. Since you plan to seal the rooms, venting some AC in the rooms would work as well. Glass does get expensive, but if you go to places like window stores and home-depot and ask for "contractor miscuts" you can get extremely good deals on expensive glass. What a miscut is, is when a contractor orders glass to a certain size, and then changes their mind, or wants a different size. The store then has custom glass they dont need, and normally sells it dirt cheap. Your best bet is to call around and see what you can find.
One more note, also pointed out already, fire escapes are important for your family and your welfare, dont overlook that! To boot though, I dont know how it is in your area, but if you do not have permits to build this, and a approved plan, especially if you dont have fire escapes, the town can have you remove the whole thing! Its pretty wild a man cannot build whatever they want anymore, but depending on where you live, they can tell you whatever they want.
Seriously though, good luck on your project, and I look forward to seeing it finished!
