* The black screen issue you see exiting full-screen mode is a bug *unless* your GUI application also performs a resolution or refresh rate change whilst entering/exiting full-screen mode. However, I don't think resolution/refresh changes are your problem, because that'd trigger when entering full-screen mode. I have to suspect an application bug here though, at least initially.
* When using the overlay-based presentation queue, you should never see tearing ever. See the README for full details on when overlay v.s. blit-based presentation queues are used. The main factor is whether the X composite extension is enabled (if it is, then blit is used).
* With the blit-based presentation queue, you will see tearing with 180.* drivers. The position of the tearing will probably vary across time, clips played, other GPU activity, etc.
* With the blit-based presentation queue, you should not see tearing with 185.* drivers. However, there has been at least one report at the URL below. Are your symptoms similar? The tearing will probably be in a constant place on the screen, and not vary.