I'm affraid that you really bricked your microcontroller and you cannot access it any more (see How (not) to Secure my Microcontroller | MCU on Eclipse for details).
With readout protection enabled and mass erase disabled the device is scured and locked and you have no way to regain access (that's the purpose of this feature).
The only way is to unsolder the device and solder a new one.
If mass erase is *not* enabled, then you still can unlock the device with a mass erase, see
Unlocking and Erasing FLASH with Segger J-Link | MCU on Eclipse
I hope this helps,
Erich
