Here's a vid clip on string serving. It is not real clear about how to start the serving, but you may be able to fix your serving by using the back serve method shown here.
You really should get a string server and learn how to do this. It will save you from having to run to the shop and waiting for your bow every time the serving comes apart. And you can use different size material to get proper nock fit.
As to the nock point. Lay a square from bowstring to shelf and put your nock pt. about 1/2 higher than level to the shelf. As you shoot some arrows, move the nock pt. down until you get good flight. Keep lowering 'til you see some up/down motion in arrow flight, then move nock pt. up a little. Then measure nock pt. with your square for future reference.