You can get more accurate ways to tell your hyperfocal distance and I have posted some links below that should help. After a while you will get to know your hyperfocal distances so you won't have to refer to them.
Link to site regarding hyperfocal distance:http://www.dofmaster.com/hyperfocal.html
Link To Printable hyperfocal calculator:http://www.dofmaster.com/custom.html
Link to online hyperfocal calculator (nice to have a play with):http://www.dofmaster.com/dofjs.html
Regarding your 2nd question then I think you are referring to the maximum aperature before becoming diffraction limited (DLA). I take it you obviously using a crop sensor DSLR ? using a 10-22mm lens but it depends on the body of your camera and not the lens. It gets lower the higher the denisty sensor so for example on a Canon 350D 8MP it is f/10.4 and on a Canon 550D/600D 18MP it is f/6.8.
Here is a site that could explain it probably better than me:http://www.cambridgeincolour.com/tut...hotography.htm
You don't need a very high aperture with a wide/very wide angle lens on a crop sensor body to get a large depth of field. For example if you had a focal distance of 12mm on a crop sensor canon (x1.6) even at f/8 if you focused at approx 3ft (91cm) your DoF would be from approx 2ft (60cm) to infinity.
Hope the above helps but I wouldn't get too tied up in things like CoC or DLA if your taking good shots.
Canon 5D MK III
, Canon 7D , Canon 450D | Canon 400 F5.6 L
| Canon 70-200 F2.8 L
IS|Sigma 10-200 EX DG OS F4-5.6 & goodies Runner up wildlife photographer of the year 2012-sunday times & winner-Canon S.A. reflection category