Need help lowering ABV

I would increase your 6 row to at least 1.5 lbs to mash with the pumpkin (if you are trying to extract some fermentables from the pumpkin). I have done partial mashes with 6-row and sweet potatoes and it comes out great. The beer might lighten up a little since you are taking out a good amount of the dark malts (which aren't really adding too much to the abv in this case). You may want to check your SRM in that case, especially since you are not using dark malt extracts (which is a good thing since they are junk in my opinion). Even cutting out some of the malt extract and adding some molasses to the beer (since you have a ton of similar spices anyway), might give you the extra sugars which are darker than the extract so they will contribute more to the "stout" like color you are probably looking for! Good luck and Cheers!