Hi Amanda, what type of screen is it? And which calibrator do you have?
Most importantly, how's your light? https://www.damiensymonds.net/2012/01/light-around-your-computer.html
Oh no, you must never never never do that! That would be catastrophic. Always preserve every precious pixel your camera captures.
To free up space on your hard drive, move the photos you're no longer editing onto two external hard drives. Do you own two external hard drives?
No, that's always been there. But as you say, nobody ever uses it, because we don't have to.
I'm stumped, sorry. I don't know why this would be happening.
I'm not aware of any setting which controls that. It sounds more like a glitch to me.
Can you click and immediately drag to make a new selection ok? Is that functionality still working?