30-40% battery drain at night
That's a known bug in android where there is no real solution for, you live in a zone with bad reception or just in between antennas.
Possible solution are: moving. Or, set your phone to 2G networks only, certainly at night. I ALWAYS put my phone on flightmode at night...

if you are rooted you can use an app for that: 2G 3G 4G switch

I read the bug is even still there in the current beta version of Android M (6.0).
I had the problem for a while but then it suddenly went away... maybe antenna transmission had slightly changed by my provider.