Ok problem solved. The problem is with the /tmp folder where a cache of db requests are kept, which is already full. I just contacted my host and cleaned up the folder.
There is no righteousness in politics. =)
Actually you can do ssh to the server provided you have permission. Then take a look where phpMyAdmin is installed, be sure to know the root.
re-check your username, password, db name. check for prefixes. some hosts require you to put before your username and db name a prefix like your domain name.
e.g. in https://www.premrara.com, db name would be premrara_prem, username premrara_premrara
I think none. But you can actually make dead easy scripts to install WP in any directory. For example a shell script to copy the files from a certain folder to another folder.