OP has a mkv going from his avatar. So 2.8 bar is correct and this is whats inside the fuel cap. I wouldn't deviate from this unless you change your wheel/tyre size.
I set my pump to 2.9 bar and it always loses some air when unscrewing the valve. After changing the tyres a few times they've all worn pretty evenly, apart from the rears which wore slightly more on the inner edges.
Using a lower pressure generally causes the outer edges to wear out faster, using a higher pressure wears out the centre faster. Check the wear on your tyres to see if your under/over inflating them.
I have summer sports tires(direzza zII), they feel terrible under 38psi. I run my fronts at 39-41psi, Rears 42-43psi and they are wearing perfectly and feel great with great grip levels. With my all season tires( mich super A/S plus) I run at 40psi all around but they feel fine at recommended 36psi.
It's better to rely on tire specs not what the car says. The car specifications are telling you what OEM settings are used.