So when I trouble shoot stuff like this, I work in this order
Connections
Hardware
Software
so, have you checked all the connections? for Screen tearing, I would check the connections from video card to monitor. Then I would swap out to a different monitor, then I would swap out monitor cords.
then I would reseat the video card, and verify that it is solid and dust free
Then I would uninstall the drivers completely, let windows manage the device as a test, watch some videos, and then I would google whatever video card you have, and "Stable Driver"