The likely reason address fields and salutations are not being pulled into the mail merge template is the user's address is not marked as the Mailing Address. It is this indicator that the code checks for to populate the information. To enable an address as a mailing address, follow these steps:
  1. Navigate to Core > Users > Edit User Profile Data 
  2. Search for and select the candidate in question
  3. Under Address, click Edit next to the home address
  4. Mark the box for Mailing Address
  5. Click Save & Exit
Once the Mailing Address indicator is in place, the mail merge should start populating all of the address and salutation information for the candidate.
NOTE: The change is not retroactive, so a new mail merge letter will need to be added to the candidate profile to see the changes.