when do I want to dry-hop this Black IPA?

I just brewed an all-grain Black IPA recipe. I have in my hands a one-ounce packet of Ahtanum pellet hops and a recipe instructing me to throw them in one week before bottling. I plan to leave it in the primary for a full month (no secondary) so does three weeks sound right? Is the idea to make sure fermentation is finished before throwing in any dry hops? Do I need to crumble up the pellets or otherwise treat them before throwing them in the fermentor?

hops don't need germ-treating. just crack the fermenter, and dump in the hops a week before you bottle, so yes, 3 weeks is right.

I usually dry hop right after primary fermentation winds down. This gives me a chance to rack off the beer to a secondary, cold crash and pitch gelatin before bottling/kegging.