Don't worry about the -12V reading, in this day and age the -12V rail isn't used, it's a legacy spec. HWMonitor also is notorious for not reading motherboard voltages properly.
The voltage on your video card also looks about right. Voltage to the GPU doesn't go too much above 1V, similar to the CPU.
You're not overheating, so I would say you have a defective card, or the heatsink is not properly cooling the video RAM if you are artifacting. Nvidia should have some older drivers on their website, though how many actually support the 630, I can't tell you. If driver rollbacks don't work, your best solution is to RMA it. The only reason the card would be artifacting like that at your temps and voltage is if there was some sort of manufacturing defect.