How many guidance counselors do american high schools have? (Read description first)

There is usually 1 counselor at elementary-middle school.
At high school's there are usually 2 depending how big it is.

At my school we have 2 full time counselors and 1 part time counselor.
The one that's head of guidance is the junior and senior counselor.
The other full time counselor mostly deals with freshmen and sophomores
The part time one deals with mostly freshmen.

As a whole counselors and how they work vary per school. I've heard some do it by year like one took over the freshmen and took care of that class till they graduated. Then I've also heard of doing it alphabetically.

I don't know if a husband and wife could work together but I think it's possible. As for requirements I think it's like a social working degree for the most part.

At my school, the students are split up into groups according to last name, and each group shares the same counselor. So there's about four or five counselors.

It depends on school size. I go to a small school so we only have one councilor for 9-12.
For requirements, I believe you need a teaching and social work degree