How in the heck do I ever find my biological father with only a nickname and city of residence around the time I was conceived. My mom (15 yrs at the time) only knew his nickname and he was married so she never went and told him
You'll have to dig deeper, possibly with the people your mother knew at the time, e. g. her classmates, if she was working then her colleagues, etc. Cousins or the like if they might know, and try to at least find a surname for this guy.