iMac only boots in safe mode, sometimes vertical red lines on display

Here we go. About a week ago I was using my mid 2010 iMac 21.5", the desktop froze. I could still move my cursor but nothing on the desktop worked.

I held down the power key to turn it off and restarted it. Upon booting the progress bar got to about 60% then the progress bar and Apple logo disappeared, then it displayed a white screen.

I restarted it with Disk Utility, ran the First Aid on the hard drive, no issues.

I reset both SMC and NVRAM. Neither of these worked, still would stop booting a little over half way through. I then booted it up in Safe Mode which worked! I cleared Safari's cache.

Curious, I restarted it from Safe Mode and the first time I tried this it booted normally but hours later the desktop froze just like the day of my original problem. So for a few days I have been just using it in Safe Mode as this is the only way I can get it to boot.

Not long after red or blue vertical stripes have appeared on the display (not solid, they're stripes which show the desktop but just discolored). Tonight waking it up the stripes are gone. While typing this, the stripes came back.

From the research I've done my best guess is it's the video card (which from my understanding is soldered to the logic board maybe?). People have said since it will boot in safe mode it must been using something in a regular boot that it bypasses in safe mode, and the video extensions are some of those things. I have tried relocating the video card extensions (anything beginning in ATI since that's the kind of card it has) to a different folder other than system/library/extensions but it won't let me because it says they are necessary. I guess this solution has worked with other peoples' issues.

I guess at the root of my question is whether this is something I should be even trying to fix at all? Obviously my computer is old. I'm looking at a costly diagnostic or repair process?

I have contacted Apple and they basically said it's obsolete so it's not something they would even look at.

If it is the video card is this something that's likely to quickly get worse to the point I can't use it? Is there any harm in continuing to use it just in safe mode?