Last time I flew IAD-CPH I was in the lounge about 10 minutes after we landed (I was in biz).
There's a fairly short walk to security (2-3 minutes) which has two lanes, then you go down half a level and through passport control and the lounge is basically right there in front of you. And since you've already cleared security and passport control, you just have to walk to the gate for AMS which is probably 5-10 minutes max.
Whether or not you'll have time for a shower is another matter but you should be fine unless the plane is pretty late. And then, as another poster said, you should be rebooked on the later flight anyway unless you can convince SK to put you on the KLM flight at 1010 or 1145.
So enjoy the lounges in IAD and CPH and don't worry too much. The worst case scenario is that you get your eight hour connection after all.