Modernism used paradox as a concept, ie. one meaning or the other is true but both cannot be, post modern reacts against that allowing for multiple similtaneous meanings. These paradigms are are discovered in different fields at different times.
The philosophy is all about subverting epistemic certainty and rejecting the very concept of objectivity. Moral relativism isn't unique to Postmodernism, but it's a critical underpinning. As is the idea to reject objective truth.
You're arguing that I do not know what I'm talking about, except this was actually my field of study. I am very familiar with all aspects of Postmodernism and as I said before if you ask the Postmodernists they would agree with my assessment, although I'm sure they'd have more positive things to say than I do.