The damage difference on a +10 TBK as opposed to a +9 is huge, almost equal to the original damage of the weapon. It's worth it to get it there, plus it more than doubles the sale value of the weapon no Teva. You would be stupid not to do it - if you need to, I can do it for you, but I won't be on until Sunday for you. For some reason I plan to be incoherent on Friday night/Saturday.
85 is a BK also. BKs have 3 levels L85, L90(TBK - Titanic), and L95(BKR - Rord). L91 HGs are a higher level weapon than BKRs. BKRs only drop from the Cursed Knight Lord and are very rare.