OK - understood
. I have used SK and NearInfinity; in my opinion, SK is easier to understand. The quickest, easiest, least-complicated way to do what you want to do, then, is when you get to the end of Tutu create a new Archer character in BG2. Start the game, and when you have finished the opening BG2 cutscene save. Open the save in SK, and change the Str,Int, etc. of the new character to match your old character, change the XP to match your old character, and save. Reopen BG2, load the edited save, and level up.
This results in a character that has all of the attributes of a level "x" Archer, all the stats/experience gained in Tutu as a Ranger, and without having those attributes during the Tutu run.
From a roleplaying perspective, perhaps your dude/dudette was working on the archer stuff on the side; the strange editing feeling was the Infamous Irenicus Torture-by-Editor
!