I've been doing a playthrough as of late simply to get the chance to kill Carth in the end of his darkside romance.

Apparently I missed a dialog, and i'm not in the mood to play again... Does anyone know a way I could use a savegame editor to change the globals to make the game think I completed the romance or those dialogs?

I am not sure but try with this:
k_swg_carth=14
g_carth_revtalk =true

One trip through the Star Forge, and nothing. These globals caught my eye...
k_swg_carthrom
carth_rom_end
end_carth_dlg
Anything you can tell me?

Would have to check the code