Blessing of fervor and haste clearly don't stack, but what about effects that they don't have in common?
Could I benefit from haste's bonuses to attack, AC, and Reflex saves, while also choosing to benefit from blessing of fervor's standup ability or metamagic?
sure, you can also choose the higher attack/AC/Reflex bonuses of Fervor while benefitting from Haste's extra attack and move speed bonus.
those just don't stack with Haste's bonuses to the same things (same for move speed, extra attack).
'stack' has a particular rules meaning, requiring modifying the same quality,
saying the spells don't stack doesn't mean both spells cannot be in effect at the same time and one dispels the other,
it just means their effects are not cumulative (stacking) in terms of how they may modify the same things.
of course if there is two spells that each only do one thing, which is modifying the same mechanic, then not stacking would mean the spells are superfluous, albeit they would both remain in effect in case one is dispelled. haste+blessing of fervor is also useful for that purpose, you can deploy BoF's options however you want, but if/when haste is dispelled, you can use it to 'cover up for' whatever aspect of haste your prefer, even if while haste IS in effect you might use it for something else (e.g. free metamagic).
RAW, I don't think BoF has anything to do with Slow like Haste does, which has good and bad side-effects.
As far as I know, yes. I've always run it that way, anyway.
They don't "stack" in the sense that you can't double up on the benefits that the same to both spell. I don't think anything stops you from getting the fringe benefits from both, though.