views filter: problems with the query object
Your add_where syntax doesn't follow the documentation given in Views code. Here is a paste : 

/**
   * Add a simple WHERE clause to the query. The caller is responsible for
   * ensuring that all fields are fully qualified (TABLE.FIELD) and that
   * the table already exists in the query.
   *
   * @param $group
   *   The WHERE group to add these to; groups are used to create AND/OR
   *   sections. Groups cannot be nested. Use 0 as the default group.
   *   If the group does not yet exist it will be created as an AND group.
   * @param $field
   *   The name of the field to check.
   * @param $value
   *   The value to test the field against. In most cases, this is a scalar. For more
   *   complex options, it is an array. The meaning of each element in the array is
   *   dependent on the $operator.
   * @param $operator
   *   The comparison operator, such as =, &lt;, or &gt;=. It also accepts more complex
   *   options such as IN, LIKE, or BETWEEN. Defaults to IN if $value is an array
   *   = otherwise. If $field is a string you have to use 'formula' here.
   *
   * @see QueryConditionInterface::condition()
   */
  function add_where($group, $field, $value = NULL, $operator = NULL) {


So basically you cannot inject a complete query like you tried to, but you must use the different methods provided by the objects to carefully construct the different parts.

The less clear part is the group argument : it refers to the groups defined in the filters part of Views UI, the one created when you use Create new groupin the filters contextual menu.