Using trees will help stretch out some of them but won't eliminate them completely, creasing is a natural part of wearing leather and nothing is going to stop it from happening. Also excessive creasing could mean they're too big.
I don't think you can reverse it. The crease comes in when your foot lands on your heel and you roll your foot forward when you walk. The more you wear the shoes, the more its gonna crease. These shoes obviously aren't shell. Shell cordovan shoes won't show any creases. If you were to resole the shoes, you could make them stiffer, but those creases will still be there. If you can't stand the unslightly creases in shoes, I'd look in to purchasing some Shells. Good luck!
Think it might just be time to get a new pair in the perfect size.