Am I correct in reading that warpriests can only treat their warpriest levels as fighter levels for their Warpriest BONUS feats (including those bought with the human favored Class bonus) and not their regular level up feats feats from race if they get them?
Yup
There's some dispute on the ones bought with the human FCB. If you can take the 1/6 of a combat feat FCB from first level then it can't be part of the bonus feat class feature. If you're required to wait until third level (when you get the bonus feat class feature) to start taking that FCB then it is part of the bonus feat class feature and gets to treat warpriest levels as fighter levels and BAB as warpriest level for prereqs.
I think the can start at 1st level/no special prereq qualification is the normal interpretation. & general feats or the human bonus feat don't get the easier prereqs either, you're right there.