GF West Coast IPA contains a whopping 15% cara- malts... and I'm not sure on this next part, but I believe it is mashed rather high when compared to it's WC cousins... Not really West Coast at all when you think about it. For the fermentables in an extract version, I'd probably just go with something more like your recipe; adding half the DME late in the boil and using 10-12% total sugar (so reduce your total DME and boost your sugar %).
I don't think it begins at 1.091 OG; that seems quite high for a beer that ends up being only 7.3% abv. I'm guessing it starts between 1.070-1.073 OG. I would want to get that FG much lower than 1.019... shouldn't be too difficult.
No need for a 90 minute boil for extract. Reduce to 60 and pile on those late additions. For the hops, they use Columbus, Centennial, and Cascade for sure. Not sure where you got Summit and Nugget from but that is not to say they might be added in small amounts and GF is simply not disclosing this info on their website. I would add Simcoe to the C hops if anything.