slowing the boat down will help like nacho said
yeah..if you're falling over backwards then you are definitely leaning too far backwards. Remember to bend your knees...your upper body will not have to lean too far back to slide the board sideways...just take a position like you are sitting in a chair. And keep the rope lower at about waist level.
As for riding switch...yeah..it feels really weird at first and will get better w/ more time doing it. try letting go w/ your back hand and that will help keep you oriented. but keep trying as it is much better to learn to ride switch right off the bat than to learn way later...like me and I still suck at it. actually..i suck at riding regular too.