Name change is denied. At this time we will not be allowing name changes on the forums as we need to manually update on a couple other places as well due to how it ties in with your hosting account (for purpose of us being able to verify ownership of an account the forum account is linked with the hosting panel account through a database lookup). You did have the choice to set your forum account when you signed up.
Regarding space, a large part of your current usage is located in Trash bin (~100mb), softaculous backup (~80mb). Backups should be downloaded to your local computer, they are of little use stored on the account if something goes wrong with the account itself. Trash bin would clean itself periodically but it can sometimes be wise to clear the Trash bin manually if you have deleted a lot of files and it makes up for significant usage (the folder called .trash would show the usage of Trash Bin).
Considering this you are however still eligible for a disk space upgrade, so I have increased the available disk space for you.