How can I assign a template to only be available to a specific user?
To assign a template to a specific user you will have to edit the database. There is a field in the templates table labeled "user_id" which by default is set to NULL. If we set this to a user id, it will assign that template to only that user.
Example command. This will assign template with ID 373 to user with id 243.
mysql> update templates set user_id=243 where id=373 limit 1;