1) Yes, that kit would be fine. Hell, it's probably better than the one I use.
2) A fuse is a fuse. They all serve the same function. The blade-style fuses are what is commonly used in automotive applications anymore.
When you put a fuse on a power line, that fuse is to protect the wire, not the device connected to it. Since the M2ATX has a 15A fuse, you'd want one rated slightly higher. 20A would work nicely.
3) 12awg would work for a short run, but I'd recommend 10awg to be 100% safe.
You need to ground the PSU properly. The PC itself should be grounded back to the PSU, so there should be no need to ground the PC itself unless you're having some unusual problems.