100% CPU load, battery drain with no app minimized/running in the background
The reason of battery drain is mostly app. Either because of poor developing skills of developer or because app is doing something it shouldn't. Well if you overcharged it for 2 hours after full charge you don't have to worry no battery is that bad to die like that I mostly left phone on charger over night and I don't have any problems, yet :).
This picture from CPU-Z is it taken just when it loaded or few seconds later, because in every phone when it just loads it show high cpu usage..?
However you should see if there is any shady app like fancy keyboards or fancy galleries try deleting them and see what is happening or apps installed out of play store.
You can use app called wakelock detector to see what is causing problem. Download ; here you can find some help about it