Thanks, I'm glad you like it :) and yes, I really regretted trying multiplayer during the middle part of the jam.
All directions should work by holding the right mouse button and pressing the corresponding W,A,S,D key.
The jarring was intentional but it definitely needs some more tweaking. My thinking was that it has to be somewhat disorienting so you have to be more strategic about it's use and so you have to keep track of which direction you're pointed to at the moment when switching again. During testing there was some flying by just rotating quickly and steering by varying the timing. So there are ways to avoid being disoriented till you can afford it ;)
Player count is also something i thought about too late during the jam...