I have a question on how you count calories in recipes where the sauce is boiled away or reduced. For example if the receipe calls for reducing the sauce by 1/2 do you count only half the calories or do you still count everything? I usually still count the whole amount but I've started thinking maybe this is wrong.

Usually reducing the sauce is boiling out the liquid (water), which does not reduce the calories. I count the whole amount.

Ok well lets say for instance tonight I made slow cooker pizza pasta that had about 20oz of pasta sauce at the start. When its ready to serve the dish is almost bone dry. Do you really count 20oz still for the sauce? Again I usually do but I'm not sure.

Yes. The only thing leaving the pasta sauce is water vapor. The 20 oz jar of sauce was mostly liquid.

Think of it like this:
One grape=one raisin. The only thing missing is the water

Same goes for sauces where you boil off the water (slow cooker recipes included)