sp:

As to the difference in pressure, when the cams are advanced the inlet valves close earlier, hence there are more degrees of compression stroke after valve closing, resulting in increased pressure.

One tooth on the crank is a lot; example: if the crank gear has 18 teeth, one tooth = 360/18 = 20 degrees. One tooth on the cams would be 1/2 that amount; 10 degrees.