You have been trying so many changes during your session and maybe your database(s) got screwed up. I’d recommend to to drop them all and recreate a empty but clean database:
# systemctl stop icinga2
# mysql -u root -p
DROP DATABASE icinga;
CREATE DATABASE icinga;
exit
# mysql -u root -p icinga < /usr/local/share/icinga2-ido-mysql/schema/mysql.sql
# systemctl start icinga2
(adapt the name of the database to your needs)