I think from reading your posts that you have removed some required tables from your master server while you were uninstalling ISPConfig the first time and that this has led to your problems. You can access your phpmyadmin here:
(where 18.104.22.168 is your IP in /etc/network/interfaces)
Here is a screenshot of phpmyadmin after a fresh install of mysql database on a Ubuntu system and also a new install of ispconfig.
The easy way you can add or remove new users is by clicking on the privileges tab - tick the "add new user" box - hit enter. You can also remove users here and request that their database be dropped to keep your system clean.
If you need to uninstall ISPConfig 3 for any reason the uninstall will remove entire dbispconfig, we need to remove only
the user in mysql database which has been created on your mysql database by ISPConfig3 during the install. The reason for not removing the ISPConfig3 user is because you are uninstalling ISPConfig3 and therefore it no longer has access to your mysql database. This is why we get the "tables already exist" error.
Hope this helps.