Why can't you strive for 100%? I'm only 4 weeks into primal and I am going 100%. I'm not planning 90/10 because I'm not planning to screw up. If it happens it happens, but if I PLAN to screw up, I give myself too much leeway. That doesn't mean messing up is the end of the world, but if your focus is on "how much can I get away with" then it's in the wrong place.
I think your diet plan is a really good one. If you follow that I think you will do really well. If Doritos is your Achilles' heel (and I love Doritos too, evil delicious bastards) then I wonder if you could get the same kind of paprika-y flavor on something else?