If a male has fathered a child, does that mean he could not have cystic fibrosis? i read that about 97% of men with cf are missing the van deferens, so if a child was conceived normally, would that exclude him from having a mild form of this disease?

If you have concerns about the Cystic Fibrosis disease, and whether you have it or not, get tested. A consult with a clinical geneticist at a medical school or children's hospital could get you proof. Genetic markers on your DNA can be examined to include or exclude any of the dozens of recessive mutations occasionally linked to the disease beyond the classical. Do the test or quit speculating.