Did you try calling them? (I certainly would if it meant saving $50.) You could also try to book directly with FM or MU.

For both legs, I suggest you try to wrap things up fairly quickly because prices aren't likely to go down. And, I'd pay a few (10 not 50) bucks more to let ctrip handle the xiy-pek leg; xiy is one of my least favorite airports in which to get stuck.