The Circle of Confusion size will influence the DOF calculations and manufacturers use different values. I've seen 0.025-0.035mm stated, Canon publishes a CoC of 0.035 in their Lens Works II and III guides, I believe Leica might use 0.025mm. It's all relative, as is DOF, there is only one point of true, sharp focus, the rest is termed 'acceptably in focus', what's acceptable to one person may not be to another. The intended use comes into play as well, 800px images for web galleries are more tolerant than an 8" x 10" print.
In your example of a 2 foot focus point, the DOF calculation using a COC of 0.3mm indicates a range of 1 foot to infinity at f/22, however there are some issues: 1. What is 'acceptable' in terms of in focus, 2. The calculations are on the borderline and accuracy is questionable, also this range is really pushing the limits of the lens, and, 3. Diffraction at f/22 has softened the photo. Apertures smaller than about f/11 introduce diffraction that may become visible, depending on the final image size that we view.
http://www.luminous-landscape.com/tutor ... tion.shtmlIf you really need a photo with everything very sharply in focus from 1 foot to infinity, you could consider a technique called focus stacking - taking multiple shots at different focus points and combining in software. I haven't used this, however I've seen macro photos very well done with DOF that can not be achieved with a single shot.
The last point to consider is sharpening and other adjustments in post processing, you might already do this but I thought I would mention it.
Just my 2 cents, there might be some other comments and suggestions that come along.