I dont understand the point of steeping it,did you mean just add it at flameout? I tend to like boil and mash because of ease and unknowingness of(difference) in outcome anyway. Adding more will get you more depends how much pumpkin. You just have to be carefull how much spice/pumpkin and when you use it as far as upfrontness. Adding spice in the boil early will put it in the background where as adding it late will bring it upfront more.How much is you add is under your control.
You can always play it safe on the spices too,taste your hydrometer before bottleing and maybe add some spices at bottleing as well if needed. Your recipe seems very bitter for a pumpkin ale.