speed bump, failed business, retired tism wrangler
True & Honest Fan
They just have to be able to respond, you can use a username and Tumblr address if you want.
It requires an address and a telephone number and optionally, an email address.
DMCA takedowns are made under penalty of perjury. You need service information of the complainer.That refers to address and phone number as examples not requirements. A counter notice requires enough information to serve someone a lawsuit, I don't believe a DMCA notice does.
Here's someone discussing this, so no you don't have to provide all of that information to DMCA someone: https://www.plagiarismtoday.com/2009/04/15/personal-info-and-dmca-notices/