I know that you have already made up your mind, but that also means that you are willing to begin from scratch, SO, before you do something else with your S6, do yourself a favor and try this one more time.
Do a backup of your files like music, pictures, videos, ringtones and others with Smart Switch for PC, forget everything else, then enter to Recovery Mode and do the wipe cache partition and then a Wipe Data/Full reset, once your device reboots, set it up as a new device, no restore from Google, your apps can always be downloaded later, then restore your backed up files and see how it behaves.
Just to give you an idea of what I think at least between the S6 and LG G4, I owned a G4 when it was released last month and after 8 days I returned it and got an unlocked Blue Topaz S6 to add to my S6 edge, and last week I got an S6 Active, unlocked to be used with T-mobile, the best 3 phones I've had in my life, this Active is now my Daily driver and it's simply amazing, giving me 9 hoirsnof SoT with all the same features, display and camera than the other 2, no fingerprint but you gain water, dust and shock resistant.
Just saying...