After 25 years in the industry I should know that there is always someone that have read more forums and researched more :)

Either way, the car is 6 years old. At this rate the battery will still be pretty fine when it is 15 years old and ready for retirement.

Never charging it above 80% is not worth the hassle. It is like never using your left hand for the fear of hurting your left hand. You are crippling your car by overthinking.