How to disconnect civi contact record from Drupal user
The answer is in the civicrm_uf_match table in your Civicrm database.  Each Drupal user is connected to its corresponding Civi contact record there.


The uf_id column is the Drupal user ID.
The uf_name column is the email address associated with the Drupal user and Civi contact record.
The contact_id column is the Civi contact record ID.


I don't know the ramifications of deleting the row which contains Drupal user 1, but you could certainly create a new Civi contact record (not yourself), and put that new contact ID in the row with uf_id 1 (replacing whatever value is in the contact_id column currently).  Once that is done, you could delete your test contact record safely.

Our Drupal user 1 is associated with a contact record named [myorg] Tech and the email address is tech@[myorg].org.  Thus our default address for mailings come from that address with no problems.

Hope that helps!