Yes, only an admin or consultant with admin privilges can delete a project from the registry and server. So, once Jeremy has received the permissions, he can proceed with the steps outlined.
Unfortunately, you cannot change the members of an auxillary project in the registry. This must be done by someone on the project. If Jeremy is not a member of the auxillary project, an admin of that project would need to add him. In the event that there are no admins or consultants existing on the project you can use the Paratext menu > Help > Give Feedback to request assistance.