Was about to post the same issue and thankfully found this thread so will just add to here that I'm also experiencing the same issue. I'm on a 2012 15" Retina MacBook Pro. When I first started the game I could choose up to 2880x1800, then it dropped to a max of 1680x1050 and now it's dropped down to 1440x900. I'm also not able to run the game in windowed mode.