You can check the data the drive itself keeps about disk errors. This data is called SMART.
https://www.howtogeek.com/134735/check-ssd-or-hdd-health-with-smart/
Figure out if the drive is having problems or not, then look at replacing it.
Another thing that slows down old laptops is thermal throttling. Once again there are plenty of programs you can download to check component temperatures. Have you cleaned dust out of the inside of the laptop and re-done the thermal paste?
Send an email to Corsair support and ask if you can have / buy some screws. They’ll probably just send you some. Worst case they can for sure tell you the length you need.
Your GPU might be having problems, but the other problems you list sound like either a bad hard drive or a virus / bad windows install.
There are several utility programs you can download that will check your hard drive for failures. I would back up any important files and then run those. If the hard drive is bad, replace it. Either way you will probably want to re-install windows from scratch.
And also are sharp enough to cut your hand if you hold it in the wrong way.