1. Yes its possible
2. Unless you want a really expensive windows machine that will look good but run like any other windows machine I don't see the point
3. Refer to 2. But honestly once you use MacOSX and I mean like really get into it without bias, you will love it.
4. Why not use the Mac version of PowerPoint? I use it all the time and I have no problems sending files back and forth and collaborating with my windows using classmates.