If I do a Factory Reset on iPhone 5, will my Service line be deleted?

Meaning I will have to reactive my phone.
I don't care about my contacts and pics w/e.

or is there another way that would help me save battery?
at night my phone is at 90%+ battery life, when I wake up, it's DEAD! Wtf?

A hard reset won't help your battery. Contact your service about your warranty or go to the apple store to discuss having them put in a new battery.

And no, your service line will not be deleted even if you do reset the phone.

No, resetting your phone will not alter the telephone and data service you receive in any way. As far as the battery issue goes, I would contact Apple and find out if you're still under warranty, they should be able to give you better information as far as that goes as there's an assortment of issues that cause battery drain.