Factory resetting is not as bad as people make it out to be. I flash ROM's all the time, and this requires me to factory reset every good i do so. Now days though, it's so easy to back up your apps/picture/contacts etc. that about an hour after you reset, your phone will be pretty much just how it was. Only thing you'll have to do is re organize your home screens. But you can back up all your apps, so whenever you go through the initial set up, it will install all of the apps for you at boot, you can back up all your pictures with Google + photos (using the Photos app), and sync all your contacts with your Gmail so they will be there immediately after you sign into your account.
This can all be done without an SD card btw
Posted via my AT&T LG G3 Running Illusion ROM