;;; Connection limits ; total number of clients that can connect
max_client_conn = 1500 default_pool_size = 50
I am assuming the difference in the port numbers between your config file and php code is a typing error.
Does the auth file (/var/lib/pgsql/pgbouncer.txt) contain valid login credentials to your database? If I remember correctly, it should have the username and password to your database.