Hi mate, have you tried to clean out the dust that could have got clogged up in the fans or have you tried to take out the card and put it in another pc and see what happens? Have you also ensured that your PCI cables are connected to the graphics card correctly, sometimes they can come out and make the screen glitch out the way you have described it. Get back to me and tell me whats happening
Was it new or new to your system? Because it's a gpu that is no longer produced and very hard to find new.
Those artifacts are signs of a dying/faulty GPU. Usually they go away when you underclock memory, but they do come back. If it is indeed new, I would try DDU to wipe out drivers and reinstall them, which if it doesn't work, you should RMA it.