well i think there are no such thing as screwups when it comes to modding save files
because you can learn from every error you make ^-^
but if you put it that way
while i was looking for the offsets where i can edit item for my star ocean editor
i accidentally found the offset for the story progress as well as the offset for the character affection ^-^
and while i was looking for the offsets for the NIER editor i found out that i found the part where the endings were stored... well i figured that out after my savegame suddenly had the D ending flag ^-^'''