I don't know what it is but I've always had problems with the Facebook apps, even now that it isn't causing me any problems I'm always cautious to update it.
I'm on my phone quite a bit, but I don't really play any games. Lot of reading and streaming music and podcast, YouTube, and other media apps. A few calls here and there texting throughout the day. Photos etc.
Ringer: silent most or the time
Brightness: 20-40 auto
GPS: only on for a handful of apps/ iAds off
Wifi: always on
BT: only when needed/wanted
Notifications: only a handful show unless phone is unlocked/ no repeat as I check my phone often enough
Mail: push is only on for my professional account, fetch hourly everything else
Background refresh: handful of apps
Active apps: I always close anything I'm not using
I still think if your not getting at least 8-9 hours of reasonable/normal use something is wrong. On all my I devices if I don't get at least one hour for every 10% of normal use I look at taking it back if a fresh install or setup doesn't work.