On the one hand, you want to find out what happened to your parents (perfectly understandable), but on the other hand Bree and Daniel need your money and car, and dumping them would probably turn them into a pair of two-bit thieves or beggars. Not good. What do I think you should do? One of the things you suggested, "cut and run". No one is even sure Jules is the girl, or even that the girl exists. And Bree kidnapping Jules? Very, VERY naughty!
In short, let's forget the whole thing and go look for your parents.
Don't let Bree or Daniel sidetrack you; shove both of them in the car and say "we're leaving, NOW!" If Jules really needs to be watched, just let Taylor and Sarah do it. The dignity has already been bruised, so don't wait for it to get worse! Get out of Texas and put this behind you! Please! 
