Re: 70% battery drain overnight, wake up and phone is dead
Are you completely stock? There might be a wakelock holding your phone.
BetterBatteryStats can help you identify these wakelocks.
I did face similar problems (not a 70% drop though, you can check out my thread
here)
Also, it's generally bad practice to use your phone heavily while it's charging as it messes up the voltage readings from the battery, which in turn displays the wrong percentage of charge, that could explain such a drastic drop.