Seattle has pretty much anything you need (except raw butter) available in a number of places. It would be helpful to know where in Seattle you are staying but this list along with what everyone else has said should help no matter where your location.
You can get grass fed meats at PCC (Puget Consumer Co-op), Whole Foods, and Madison Market. Madison Market (Central Co-op) has one location in Seattle. PCC and Whole Foods have multiple locations throughout Seattle. There are also specialty meat shops which you can google which also carry grass fed meats and even mangalitsa pork.
Obviously the above places also carry seafood, organic produce and other items that may suit your needs. While there are other options the above should pretty much take care of whatever you might need.
Pike Place Market in downtown Seattle carries raw milk (Pike Place Creamery) as does Madison Market. Whole Foods does not. As one person has already mentioned there are a number of Farmer's Markets in the area open at various times during the week. You can find pastured eggs at those markets and also raw milk but arrive early as they sell out very quickly.
If you drink beer the most extensive collection will be found at Whole Foods, including gluten free beer. As for wine there are numerous great shops throughout the area. If you want a recommendation let me know.