First of all, I wouldn't waste my time with the Candi Sugar. If you want real dubbel-type flavor, then you need Dark Candi Syrup (i.e., D-180). The candi sugars don't do much (if anything) on the flavor side.
If it were me, I'd definitely cut out the Caramunich and Wheat. If you change the candi sugar for dark candi syrup, you can probably skip the Carafa. I love Special B in a dubbel, but 12oz might be a bit much - a little goes a long way. Maybe drop it to a half pound.
The Biscuit I can go either way on. I like what a touch of Biscuit or Aromatic gives to the dark Belgian styles, but I generally skip it in dubbels, and reserve it for my Quads where I want to develop a little more malt complexity to stand the test of time. A half pound would certainly be appropriate in this style if you like it.
A great dubbel recipe is the one for La Trappe Dubbel on the candisyrup.com site (http://www.candisyrup.com/uploads/6/0/3/5/6035776/la_trappe_dubbel_-_variation_003x.pdf
). The combination of the D-90 and D-180 syrups gives a real nice complexity. It has become my SOP for my dark Belgians.