Well, the class states that you get spring attack for free even if you do not meet the prereq (but I think that the prereq for the PrC itself assure you you meet the prereq for spring attack anyway). But anyway, the prereq is bab +5 and spring attack is given at level 3, so you DO have bab +8. I see no problems there.
The point of having scimitar treated like a light weapon is not so you can finesse with it (since with my suggestion, you could finesse with it anyway). The point is to have a light off handed weapon to have -2/-2 instead of -4/-4.
cd saint, if ITWF is your 6th level feat, you are cheating. It requires bab +8... [edit: sorry, just saw that in 3.5 it's +6]