> Also I thought the Klingons were part of the Federation at one point during DS9 era? Or perhaps that was just an alliance...

There was indeed a military alliance between the Federation and Klingon Empire against the Dominion. A friend of mine (uncharitably) referred to the war against the Dominion arc as the writers, "exploring what Star Trek could be... if it was more like Babylon 5."

And then we discovered that it was all really just Ronald Moore preparing for what eventually became Battlestar Galactica. Weird pseudo-religious nonsense included.