Pumpkin/Buffalo Sweat Clone Partial Mash Questions

Hello,

I will be doing a 5 gal Partial Mash Recipe kit of the Buffalo Sweat Oatmeal Stout (from Northern Brewing site). I read on another forum here that there is also a pumpkin version of it. What I'm planning on doing is following the Buffalo Sweat recipe until the end of primary fermentation.

Afterwards I was thinking of transferring 3 gal into my glass carboy for secondary fermentation, and leaving the 2 gal in the plastic and adding the following:

1/2-Tablespoon of ground Pumpkin Pie Spice (or canned pumpkin?)
1/2-teaspoon of ground Allspice
1/8 teaspoon ground nutmeg
1-cinnamon stick
2.5-cloves
Vanilla extract

My questions are:

1) Do I just dump the canned pumpkin in and then close it for secondary fermentation?
2) How much less of the spices above would you use for a 2 gal? Just 40% of the numbers above which are for 5 gal? Just dump them in for secondary (no tea bag or cheese cloth needed?)
3) Do you think priming the 2 gal with brown sugar would add a nice hint to it?

Thanks in advance for any help you can provide!