Use a thin rubber/elastic band or even use a latex disposable glove. Put either item over the screw head then use a regular screwdriver as normal, perhaps use a little more downward force when turning to ensure it grips. It should come off that way. Use a screwdriver or bit that fits snug, don’t use one that is too small or too pointy, as they can be different etc

Try and source a new screw to replace it rather than using this one again.

Does the SD card slot flush with the laptop frame when put in, or does it sit outside it a little? If it’s the latter it could be that you’ve bumped it in transit and you have broken the connector off the motherboard. It can actually be fixed if that’s the case, it just might not be worth it when you can use an external reader via USB also.