Sadly, I think I'm giving up. I managed to flash back the original stock, and I think even that was a miracle. Not surprisingly, after doing 1 update, it couldn't do any of the others. So I got the 2020 version of stock, which should have the proper update, and tried to flash it. ADB worked fine, Fastboot identified the phone after reboot into bootloader, but then fastboot would just stop working. Neither the flash_all nor trying each flashboot command manually worked. The operation was just suspend. I would leave it a long while just to make sure it wasn't like when the percentage stops