Electronic – What loading capacitor do I use for the crystal

A good tip for getting optimum cap values is that an oscillator like this is happiest when the amplitudes of the signals at each side of the crystal are similar. PCB capacitance will be a factor, so this needs to be tweaked on the actual board, and using a x100 scope probe to avoid the probe affecting the reading. A 10M resistor right on the tip of a standard probe is an alternative if you don't have a x100 - accuracy doesn't matter as you're just looking at relative amplitudes.

You need to add a capacitor to each crystal terminal making up a total capacitance of 12.5 pF, including tracks etc. The two capacitors are effectively in series, so you need something like 20 pF.