So I attempted to add the new dawnguard bows and arrows to a vendor in my mod and tried testing it out thinking people with dawnguard could buy them and people without dawnguard just wouldn't be able to see them as they wouldn't have the items in their game.

I found out after testing that not having dawnguard would instead cause skyrim to crash if they had my mod enabled. So i deleted everything I added to my mod from dawnguard, but it still crashes and when I load my mod on the CK it still has Dawnguard.esm listed under the Parent Masters. How do I get rid of it?

Select your mod as usual (make active). Where is says master files (top right hand side) select Dawnguard.esm, hold Ctrl and press delete. Ignore warning. Continue to load mod and save it again.

Consider using getformfromfile to add the inventory from dawnguard to the vendor via script. I'm using it to do a lot of dawnguard asset use if dawnguard is available without having to have dawnguard set as a required file in the ck.

OMG thank you so much, I'm sitting here trying to right click dawnguard.esm and find a delete or not holding control and press delete