It seems your code puts you in CDC mode, so that’s good. The bad side is your driver failure. That’s what you need to sort out.
The device will stay in CDC mode until you erase your code from the device, or until you can get the driver installed. So right now, you’ll need to but into bootloader mode and erase with Tera Term (perhaps that will require you to reload firmware too) so you can get back normal access to the board. Then you still need to sort out the drivers !
Tell us (or show us) exactly what device manager sees so we can be sure what you’re up against. And also tell us about what you did when you were asked for the driver, did you locate it on your PC?