Actually, the Savegame Editor's backup disappears if you save over it just once. That's the way the Divine Divinity savegame system works -- it overwrites the entire folder. So if you make a change in the editor, make a backup in .000 format, and then save the game again, the backup file will be gone.
You're right though. It is probably easier to add the constitution points, but I think the editor only allows up to 100 points, even with the "redistribute" option turned off. That might not be enough for a mage to get out of the dungeon, since they receive less vitality bonus for constitution. Who knows... best of luck to ya if you decide to fight your way out of Iona's at 11th level. <img src="/ubbthreads/images/graemlins/up.gif" alt="" />