Welcome to the forum! Great first post. Your recipe looks great.
One piece of advice: If you really want this to taste like peanut butter, I've found that there is little else in the world that tastes more peanutty than some toasted Maris Otter. Put 2-3 pounds of your base malt into a 350 F oven for about 20 minutes prior to brew day, and you'll have a very nutty beer indeed, even without adding any PB powder. It will get your beer 3/4 of the way to where you want it.