if you don't actually need to doctor, but only need to remove the theme, you may be able to do that with WOSQI or Preware.
WOSQI has an unofficial release available on the forum (v. 4.5.1). you put it on your PC and then connect your device via PC. the device must be in dev mode first.
Preware i believe also requires devmode, since you install it to your device with WOSQI. They just released an update which was the purpose of rushing the unofficial version above.
I believe either will allow you to delete the theme. I've never used a theme so IDK. Just another option.
But a completely fresh start requires a doctoring. You download the doctor and the novacom drivers to your PC, and connect the device via USB. But this time the device must be in recovery mode before connection.
once you get Preware or WOSQI, you should install internalz pro, which will also request the accompanying file manager. this is what you want on your device to install/edit/view/explore files.
All of this is explained here and at webosinternals where you select the doctor for your model and carrier. good luck.