Having trouble exposing custom table with relationship to multiple entity fields

Question

I have a custom table with two fields I'd like to use as foreign keys to user with corresponding content fields attached to the user entity. So far I have the base table exposed to Views and showing data in preview. I have been trying to add just a single field of relationship/join at a time, so here's what I've got for that:

$data['lcm_subscription_lookup']['SID'] = array(
  ...
  'relationship' => array(
      'base' => 'field_data_field_subscription_sid',
      'field' => 'SID',
      'handler' => 'views_handler_relationship',
      'label' => t('User SID'),
  ),
  ...
$data['lcm_subscription_lookup']['table']['join'] = array(
  'field_data_field_subscription_sid' => array(
      'left_field' => 'field_subscription_sid_value',
      'field' => 'SID',
  ),
);

I think there's a clue in the views generated SQL with error:

...
FROM 
{lcm_subscription_lookup} lcm_subscription_lookup
LEFT JOIN {field_data_field_subscription_sid} field_data_field_subscription_sid_lcm_subscription_lookup ON lcm_subscription_lookup.SID = field_data_field_subscription_sid_lcm_subscription_lookup.

Note that there is no field specified (empty string after "." where I'd expect 'field_subscription_sid_value') in the JOIN .. ON to the field table.

Once this is working, I'll need to also add in the other field (lcm_subscription_lookup.AddrID -> field_data_field_subscription_addrid.field_subscription_addrid_value) and then what to link to the User itself?

This https://drupal.stackexchange.com/a/137661/2114 looks really close along these lines, but I haven't make the connection.