Same issue here. Running Kivy 1.9.1 on Raspbian Jessie on a Raspberry Pi 2 B with official 7" touchscreen.
I altered the kivy install's config file to try to force it to a window, but even when I set fullscreen to 0 and width to 400 (half of the default 800), no change. The config file handled other changes to the modules and input section fine.
Honestly, though, I think the bigger issue is that it doesn't close properly back to X. The only way I can get the app to close reliably is by adding a close button that kills the app, but it doesn't go back to X, it just stays as a dark screen. Then I have to disconnect power to the Pi without a proper shutdown and risk corrupting the SD card. Not an ideal way to debug.
Ctrl+C only works very intermittently for me as well - when it does work, it actually will take me back to X, but I'm not sure how to get a normal app exit to do that.