Unable to update data from federated table automatically
You can create an event as follows for calling stored procedure in every 5 minutes. 

CREATE EVENT myEvent 
ON SCHEDULE EVERY INTERVAL 5 minute 
DO CALL myProcedure();


Here i am creating full process of executing an event with example.

step 1: checking user permissions.user should contain grant permission as     follows.

   show grants for root@'localhost'\G
   Result:`GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY PASSWORD '*81F5E21E35407D884A6CD4A731AEBFB6AF209E1B' WITH GRANT OPTION.
step2: creating an database with two tables as you mentioned tab and fed_tab.

step3: Creating and executing  stored procedure.

DELIMITER $$

DROP PROCEDURE IF EXISTS `HOD`.`fed_procedure` $$
CREATE DEFINER=`root`@`localhost` PROCEDURE `fed_procedure`()
BEGIN

  declare tab_indx integer(11);

  set tab_indx = (SELECT id FROM tab order by id desc limit 1);
  insert into tab select * FROM fed_tab where id&gt;tab_indx;

END $$

DELIMITER ;

step4: Creating an event. 

 CREATE EVENT myEvent 
ON SCHEDULE EVERY  5 minute
DO CALL fed_procedure();


it is successfully executing in my machine.the main problem of yours is permission of root user.