Could anyone tip me off as to how many millimeters of brake bias turnbuckle do I want exposed to achieve 40%f/60%r brake bias? What about 50%/50%?

And is it normal for the brake pads to have an indentation from the disc in them after their first race weekend?

How long do brake pads typically last?

Sorry for all of the nitro newbie questions. Thanks in advance for the help!