Sprint is awful. You have to be in a city where they've launched 4G before you'll see it.
4g LTE is different from 4G Wi-Max. Your phone is LTE, not Wi-Max. They have like 7 markets with LTE
The Commandments of Android
1) Open RAM is wasted RAM - Don't use Task Killers
2) Cheap devices are cheap for a reason. Don't expect high end performance.
3) Boot Loop = Wipe.
4) There are no viruses for android.