I just tried to recreate the softlock, and what in the world? This bug didn't exist when I released the game in the Spring. Dozens of people played it and had no problem. But now I'm experiencing the exact same softlock as you.
I have no idea what's happening with your windowed vs fullscreen mode, I can't recreate that at all. But I guess the game is unplayable until I have time to dig back into the game's code and re-compile everything, which I don't have time to do right now. Sorry :(