This is a familiar story. My daughter has a 2005 Focus with the same issues: relay clicking, dash lights flicker, radio loses stations, headlights went crazy once . I knew it was some type of bad ground but she was too far away for me to help her. She finally located a small shop in NW Tennessee that diagnosed the problem. Can't tell you the name of the part, but it near the PCM and it was corroded. They replaced it and that fixed it. After two years of living with this. When she return home I'll ask her the name of that part.