1) There is a 99% chance that it will solve all your game issues. If it doesn't, the issue is probably a bad rip.
2) Greater brick protection than just BootMii/Priiloader (due to the patched system menu). Being able to play any new game you might purchase without having to update your mod (as it will already be upgraded). Just being up to date.
3) You'll probably want to use FAT32, there is a link in my sig for that. There is a sticky for each of the three main USB loaders (WiiFlow, Configurable USB Loader, and USB Loader GX) on this site. A good search will find those for you pretty quick.