Webber turning into Maldonado? Not quite. Sure, some of his moves were iffy, and his driving as a whole poor by his standards, but he’s still a ways from full-on Maldonado madness. (And to be fair to Pastor, his driving has improved since then.) As for whether there was a financial motive, I believe the more likely explanation is that Webber, mathematically eliminated from the title race, figured he had nothing to lose.
The performance bonus is presumably an incentive for the individual drivers to perform – reward for work, work for reward. That way, if both drivers excel, RBR maximize constructor points earned. It’s a way of guaranteeing that the team gets ahead in the WCC, and the drivers get up there in the WDC.
Webber has always accepted team orders reluctantly. Why would he would be so unwilling if there was monetary incentive for supporting Vettel?