I can help with a few of these!
!. I used fleece for my first bat suit for the wings, and flannel for this next one I'm working on (since I need to dye a design on the wings and fleece does -not- take dye nicely)
2. Depends, if its foam I'd use wire, resin springs. If foam, I did a mock up test and found this way seems to be the most sensitive option
http://fursuit.tanidareal.com/savoy/en/03fmakeheada.htm3. It's up to you and what the design is going to be. My first bat, I made the wings part of the arm, and the hands separate and would grab onto the wire part of the wing to open it up all the way. This next one I'm working on, the commissioner wants two fingers out, the pointer and the thumb, and the other fingers hidden, which I'll probably just make a mitten like-thing for the other 3 fingers.
For my first bat, I used wire coat hangers that I coated wit rubber to cover the sharp edges. Some people use wire, maybe 12 gauge or thicker.
Here's my first bat
http://www.furaffinity.net/full/20755780/And the concept art of the one I'm currently working on
http://www.furaffinity.net/view/21488860/