re: Angled dado?

If your going to do multiple cuts you would have to make your first cut (at full depth)  then move you fence and lower the blade.  You will have to sneak up on the height, raising your blade a little at a time, until the bottom of the cut matches the first cut.  
I would rather set up my dado blade to the right width and then run the full cut in one run. 
Side note,  you can set the width of your dado blade while the blade is in the 90 position to make it somewhat easier to run sample pieces until you get it right.