I have a Shimano tool that is similar to the BBT-9, but open ended. I have never worried about the amount of torque on the bottom bracket. I put lots of anti-seize on the threads and run it in till it contacts the bottom bracket face, then just tighten a bit more. I have never had one come loose.

A steel tool on an aluminum cup will usually mar the aluminum cup, but its just cosmetic. If you want no scratches on the cup, use some sort of buffer like a piece of thin cloth or tape between the tool and the cup.