Replying to Before I start filming

Next winter I'm planning to start making edits. I only own a gopro hero 3 black and my friend has a Nikon D5100 dslr and I'm wondering on how should I combine them in a single edit.

The Nikon shoots 24p, 25p or 30p. Which one should I use?
the Gopro shoots 25p to 60p. Is it meaningless to use 60fps since vimeo and youtube don't support 60p?
Should I use protune?
Should I film at 1440 4:3 and do the dynamic stretching thing?