First thing is advice from The Hitch Hikers Guide to The Galaxy: DON'T PANIC!
These cards are quite robust and 80C is not a problem, over time it will creep up and the fans/s will run faster, this is normal and just indicates a little dust build up on the cooler, again, nothing to worry about and easily cured by a quick clean. In fact if you have several pets in the house or live somewhere dusty, you should clean the card and CPU cooler, every 6 months or so, there is plenty of Youtube videos on how to do this and it's not hard.
Don't get worried about GPU usage, they are DESIGNED to run at 100% use. For years.
It's actually better to run the system 24/7 rather than turning it on and off-sounds odd I know but industrial systems run for...