You guys are just mean
Aah, you say the nicest things

#16 -- religion will be influenced by those things, but also religious buildings and agents, and those in neighbouring provinces - "faith propagation" does leak across borders. I don't know where the minor ones come from, probably just a residue of the owner's culture not exerting maximum effect at the beginning, possibly related to the rebelliousness quotient, too.

#17 -- I didn't know about 3 provinces for clansmen bonus either! As you will have gathered from this, more than one province can give a bonus, but IIRC only one will show the tooltip for it on the province parchment, same as multiple units in one province, only one unit will show on the parchment (hence the "hidden" bonus for assassins in Syria)