Your npm error can be because your npm isn’t installed correctly or you are using nvm for example.
The rig will only look at the basic npm install path (see Barry’s answer for more detailed information)
About deleting an extension, there is a known bug where you can’t delete an extension that doesn’t have a version in it. Create a version on the dev site, then delete the extension
It looks like you are using a mac, make sure you have the latest version 1.1.4. before the 1.1 version the auto update didn’t worked properly. Since then, there was a new video component design that was published. Preventing the use of the old video component design.
The rig 1.0.3 still ask for the old video component design, resulting in an error