It's entirely possible to have your username altered - many of the forum's users have done so, myself included. As for content purging, I'm not so sure, but it's generally more favourable to remain on one account unless there's a technical reason preventing you from accessing said account. Since you don't have many posts on this account, it might be worth instead going back yourself and editing your old content to simply 'BLANK' or something similar. You can view your own posts from your profile and access them in that manner, shouldn't take more than half an hour to go back and clear away your shame
But, to sum up: keep this account, remove the old content yourself, and PM a Staff member to get a handle change. Far more efficient, and it'll save on having an un-used profile on the forums.