As this is your first go round, I would just let it ride and add your priming sugar and finished beer into the bottling bucket and package it up. Next time you brew this, take your notes from this first batch, and increase the amount of PB2 to get your desired effect.
The only reason I say this is because if the PB2 didn't dissolve fully in the kettle and fermentation, then it definitely won't dissolve well in your bottling bucket which could potentially ruin what you have already worked so hard to create.
BTW, let us know how this one turns out. A buddy of mine used that PB2 in the past for a beer like yours and came it out pretty interesting. Not much head retention though...