Few questions about relations

1) what number does my relation with a faction have to be in order to buy gear from the factions merchant

2) how does commner trust work. I know how to lose it but I'm looking to gain it (I know rescuing prisoners is what most do, but recruiting from villages helps in sieges)

3) despite having positive relations with all religions, will this really matter when recruiting? Because I've had positive relations with the seven and rhollor but only able to recruit from rhollor villages because that was my characters religion

4) How much relation do I need with the high septon so he can bless my wedding between me and my horse.