Sounds to me like you now have your problem. It's highly unlikely shutting things off will help your video card.

Any chance you can have Lenovo come back out and replace the video card?

Well the whole thing is under warranty, but I'm not sure what I would tell them other than "it doesn't seem to be working right," which is somewhat vague. Would there be diagnostics I could run that would provide evidence that it's gone all toasty.

Also, vid cards are soldered onto the boards on laptops, I think, so I think I'd have to send it back to them for work, and I can't be without my laptop d.t. work needs.

If you have in home warranty service, don't they come right to your house and do all the work there?

That's what they did with the fan. Not sure if that's work that can't be done at the factory. I'm going to look into it though. Maybe they'll just say screw it and give me a whole brand new one :D

78 is within normal limits for a laptop. They run hot. I would maybe updated video drivers or mess with settings. Maybe shut down all non essential process and run EQ and see if that helps.