"... supposed show was in 1990. This sounds extremely unlikely since Oprah was not a nationwide presence at that time."
Obviously you didn't excel at math .. because Oprah just celebrated her TWENTY-FIFTH YEAR.
Just walk away, please...it is painful to watch you.
Not as a nationwide tv show she hasn't.
My math is fine much better than your eyesight which conjures up shows THAT NEVER WERE SHOWN. The only question is Why?