Hi Beth,
Look like it's already been covered after quickly glancing through these comments to your post - especially those comments on focusing, framing and recomposing. I can assure you that F/8 in this situation (having done studio work) will normally get the entire head in focus, but not much else. You have to use the techniques suggested...
Another option is to consider separating the AF and shutter release functions. The only downside with that kind of setup is in portrait mode, especially with a battery grip: the AF button on the back is a fair distance from the shutter button. If no grip, it's hard on the wrist if done repeatedly. However, getting this issue resolved is first priority. We can cover my suggestion and it's rationale another day...
Regards,
Marc