IANAL. First of all a cease and desist doesn't require you to do anything. It's merely a threat. That said it seems pretty clear that you're violating copyright laws. The DMCA only applies to user generated content (UGC). You're not letting users input their own links to 3rd party content, you're finding the links yourself. It doesn't matter where you get them from. Not only that but you're not linking to this conten…
I wonder how can he be violating any law with respect to distribution of copyrighted content when he is not distributing anything. He is just pointing to other sources doing the actual distribution (which may be legal). He is just providing links, although with a nice interface.
Sadly, the Internet isn't our playground anymore. You have to watch what you do even if it's just curating links to things you can download for free.