You just need to mess with the Y axis of the layouts for your paralex backgrounds that you've already edited the X axis for. At the moment they're set to 100 (default). Its impossible to tell you what's the right setting until you build more of the level upwards or downwards, so keep doing that and then just mess with the Y setting until it looks how you want it when the screen scrolls
Shouldn't be too hard. You have the X axis looking pretty good already