The contribution for the C40L is ONLY if you mash it... Since you're not, it gives you very little (if anything)...
I would get some light DME to use.
Software really helps when you start formulating/changing recipes. Since you're making an extract brew, you can't count the specialty grains. You would only be able to count them IF you mashed with some base malt too. I would also keep the C40L contribution under 20% of the recipe. Most of the time, you don't see more than about a pound of any single specialty grain used. Also keep in mind, most DME/LME include other malts in them. So, you're already getting some crystal malts with the light DME (more with amber DME)...
Making something like this would be far easier to figure once you go all grain, IMO/IME... Since you'll know, for certain, what grains you're using, you'll have a much better idea of color and such...
I really would run the entire thing through software before you go back to the HBS. That way, you can get more DME if you need to. Either use one of the online tools, the open source software, or get the trial version of BeerSmith (you get to try it out for 21 days before they want you to purchase the license)... It's [BeerSmith] been a huge help since I started formulating my own recipes.