As far as why women get paid more in porn than men, well it's sort of obvious.  At least 70% of the consumer base for straight porn is MALE (maybe higher).  The customers don't care about the men, they just want to see "pussy."  The men are just there as props.  Go read Jenna Jameson's book, or even Nina Hartley's website where she answers questions about the porn industry.  They pretty much say that men are only there for props.

The industry pretty much goes where the customers are, not where they COULD be.  Which means they churn out globs (yeah that entendre IS intended!) of dumbed down straight male oriented porn so men can run in & buy some cheap shit, not look at the cashier when they buy the crap, go home & secretly jerk off & then go to the Baptist church in the morning.  And most women?  Well they just deny whatever sexuality society deems "appropriate" for them.