Battery drain even on standby, AT
I seem to be getting somewhere around 10% battery drain per hour even on standby. I've not upgraded software recently because I'm still on iOS 9.1. It was working fine until last update of Music App(1/30/16) which started to drain battery with "background activity," something I've never seen before on previous update. I've already setup my phone so that it's not losing battery such as background refresh, manual email fetch, brightness to 50%, limit ad tracking, wifi assist, turned off cellular data for certain apps I don't use, calibrated battery, etc. So far nothing worked so I reset my phone to factory settings and set it up as new phone and I DID NOT restore from my backup in case my backup is corrupted. So far it's been few hours since I reset my phone and I have not installed any apps back on my phone, but I have not seen any changes.
So I have two questions:
1. When I setup as new phone can I use the same icloud email address I used or do I have to setup a whole new icloud email?
2. After resetting the phone to factory, am I suppose to see the changes right away or does it take few more charges(few more days) for my battery to settle in?
iPhone 6, iOS 9.1