tiopaco

Dont worry, the card will throttle at high temps, preventing damage, and will shutdown if too hot

You could idle at 75, and as long as you don't go over 85 under load, you'll be a-ok.

That's pretty cool man, GPUs typically run around the same heat as a CPU so as long as your not really going above 85C your good though I would prefer to stick near 75C. I would only add a case fan if I'm having issues with keeping it cool under load, or if the fands are having to really ramp up to spin and I'm not enjoying the sound. You should also be able to set a fan speed curve to control how much your fans ramp up as the card warms up, and just requires some testing and tweaking.

Its fine, could be lower, but doesnt damage the card in any way