You need to make sure drush uses the exact same php as MAMP is configured for. Start with
and make sure it is the one configured within MAMP. Edit the PATH variable in .bashrc or whichever other shell config file you have active on your Mac account. Your screenshot seems to imply you've got this covered, but double check nonetheless.
and check whether drush fully bootstraps Drupal, indicated by successful connection to the database. (BTW: You should not connect to the database as root, not even on your laptop.) Run this inside sites/default to really be sure you are picking up every bit of configuration detail while you figure out issues.
As a last resort follow up on the links your error message spewed out.