Secondary stats (det, crit, speed) are an issue of some debate. General wisdom in the past has said that det > speed > crit. Personally I see merit in all three and blend accordingly.

You can use the book multiple times and it will reset the points of the class you are on.

Putting 30 points into mind is a safe bet. Some WHM prefer to shift some points into vitality as to survive certain mechanics a little more reliably, with the reasoning that a few points over to vitality does not affect their healing output very much, while offering a buffer against certain mechanics like turn 5 fireballs. My own opinion is that the extra health is not needed and the always-useful bonus to healing that mind provides does the greater good.