Make a bootable windows 10 usb key / drive and plug it in while starting, when in the boot menu there should be a logo on the right of the android one. I cannot help further since i do not own one but I think you just have to install windows that way. Be careful not to delete android while reinstalling windows.
I know it might look stupid, but next time use a flashlight and put it really close to the screen, you should be able to see (if the tablet is turned on) a really dark image, but that’s normally enough to set the brightness to a higher percentage.
