We appreciate your effort. My comment is on Step III "(f) If you've to officialy repair Crater, fully unroot in SuperSU".Will Super SU remove twrp and reinstal stock recovery? I am not sure it will. Also the binary count will be custom. You have to use Triangle Away to reset binary count.
If not and If you take your crater to service center for warranty repair then you will still lose warranty as you have to install back the stock recovery. TWRP will result in System Status as "Custom".
IMHO the best thing to do to claim warranty repair is use triangle away to reset counter, flash the stock firmware using ODIN, factory reset after flashing to bring back system setting in download mode to official..Please add these steps to your post.