DB Error: connect failed when trying to call Job.execute using cli.php?
First, you can view the error with greater detail if you enable "Debug and Backtrace", or view the CiviCRM log.  The troubleshooting documentation will tell you how to do both.

Second, I would assume that "connect failed" is a MySQL error.  Is it possible that you have two civicrm.settings.php files in your path, one with the wrong MySQL password?

Finally - yes, drush and cv are additional tools to install.  However, if you're administering Drupal/CiviCRM through SSH, these tools are amazing timesavers.  Configuring cron with cv or drush is 10 times easier than what you're doing here, even if you factor in the overhead of installing drush or cv.  Drush in particular will give you a number of other command-line superpowers - you'll be glad you installed it.