As written, you've got about half a Robust Porter. If you add a half-pound or so of 50-60L Crystal malt to your grist, you'll be better off.
What you do
not have is a Dry Stout. There is no room in Dry Stout for black patent malt or chocolate malt (or crystal malt, for that matter). There are three ingredients in a Dry Stout grist - pale malt, roasted barley, and flaked barley. Avoid crystal malt for body and mouthfeel; those characteristics should from the flaked barley.
Each specialty grain provides certain characteristics - flavor, color, and (possibly) fermentables. Those characteristics make them appropriate for certain styles. It is impossible to approximate the characteristics of a certain grain by substitution of others. You simply cannot hope to approximate roasted barley with a mixture of black chocolate malt; it just doesn't taste right. Try tasting the grains - crunch them up and eat them - separately, then in your proposed admixture. You'll soon agree with me.
In Dry Stout, not only does the roasted barley provide color, it provides flavor and a proportion of the balancing bitterness. You can approximate the color with a mix of black and chocolate malts, but not the bitterness and never the flavor.
Sorry to be so negative, but you
did ask.