If there are any bicycle frame builders in your area, they will have the tools and knowledge to know how to cut and install headsets properly. The fact that he didn't know what the spacers were for was a good indication he knew nothing about how to install the threaded headset you gave him. The fact that he scratched the adjustable nut showed he didn't know what tool to use. When you spin the fork in the frame, it should move freely but not have any play. Can you check that and get back to us and let us know that it does rotate smoothly without any tightness but at the same time when you hold the fork and try to move it back and forth, is there any movement or play? I will be surprised an inexperienced mechanic knows how to get that right. Again you might take it to a framebuilder to get his impression if the headset was installed correctly. He could at least make sure the top 2 nuts were correctly adjusted. I'm suspicious they were not.