re: Angled dado?

Ditto. Set the dado width, set the angle, then make some test cuts on cutoffs and double check it’s what you want. 

Alternately, you could follow your original plan with a single width blade, cutting the full dado, then roughly clean up the bottom with a chisel. After glue up go back and band the edges and you’ll never see it. More steps, a different look, but another way to skin it…