Okay, so.
1) I find it unreasonable to change the internal username. To begin with, I haven't seen services that allow chaning the login username for its users. Just changing the screen name is enough.
2) Maximum that I can do, is to reassign your music under your previous account to Varin0x and remove previous assignment as a result. We do not delete music already in the archive on such requests. for further info, please refer to this article:
https://modarchive.org/index.php?faq-removal-policy3) I will disable your previous account after you provide proof you're the actual owner of it
Cheers