2011 iMac 27 inch - game performance is very poor, and no difference between fullscreen/windowed?

I'm running the following:
2011 27inch iMac
OS X Version 10.8.5
Processor 3.1 Ghz Intel Core i5
Memory 8GB 1333 MHz DDR3
Graphics Card AMD Radeon HD 6970M 2048MB
Display Resolution 2540 by

Game performance is very poor. When I'm in the pregame menus, everything is 60FPS so that's fine. When the game itself starts (so I can see the planet, but I haven't spawned a commander yet) the FPS goes to 30. When I actually spawn the commander, and zoom in on him doing nothing, my FPS becomes 15, where it stays for the rest of the game (though sometimes dipping below 10FPS in battles). I've tried this on multiple planet types with different settings and it's pretty constant.

My ingame settings are everything Medium, with HDR and AA set to "Off."

I see the same behavior on both "Fullscreen" and "Windowed" though I can't actually tell a difference between these two modes - the game seems to be "windowed" in both cases (ie, in fullscreen I still see my OS X dock at the bottom of the screen, and the top of the application has the typical bar with the green/yellow/red OS X buttons (see attached screenshot). Is that expected?

So, in summary, two issues:

1) Game performance is poor on all Medium settings, averaging 15 FPS.
2) "Windowed" and "fullscreen" modes are both windowed. I can't get fullscreen to take up the entire screen, IE hiding the dock and removing the top bar (see attached)

are you running steam version? there is a steam issue still running around (There is a thread around here somewhere telling you how to fix it)

As for the windowed thing, that is a OS X thing, it has to do with how Uber is doing fullscreen (it is just a borderless window, rather than traditional fullscreen) which means right now on OS X it appears windowed in both cases. uber should be fixing this eventually.

EDIT: This might help https://forums.uberent.com/threads/how-to-improve-frame-rates-all-video-cards-driver-links.53165/

Fullscreen not yet implemented for Mac/Linux.