Hire a copyright attorney to help you make sure that you are following the proper procedures and requirements to take advantage of the safe-harbor provisions of the DMCA. In the meantime, a web hosting provider have put together a flowchart of how it handles DMCA notices that you might find useful at http://blog.nexcess.net/2012/02/22/dmca-process-infographic-flowchart/
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You been asked by an [alleged] copyright owner to do far more than what you're required to do when you recieve a DMCA takedown notice. Which means that you are NOT simply being asked -- as a mere conduit for someone else's infringing activity -- to take down some copyrighted content. You are being asked for information to incriminate YOU in a potential infringement claim against YOU. Which sounds right because it appears YOU were the one who published inline links to allegedly infringing content. You need to hire a copyright attorney to evaluate the situation and to, perhaps, respond to the copyright owner's email. You should not respond yourself because you will likely make admissions that can be used against you. Good luck.
The above is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.
That is not a mere DMCA take down notice, since they are also asking you for information on usage and revenue. Consider it as if the cops were asking for a confession (which this might, in fact, be!) Your are being investigated, perhaps by law enforcement, but more likely by a copyright enforcement attorney. That is a copyright infringement notice and they are seeking to get you to give them evidence to use in making a copyright claim against you. Likely, they are doing it as warning shot without really expecting you to voluntarily provide the requested information, which you would be very foolish to do at this stage. If you were actually sued, you might have to produce such information in discovery, which might occur before trial or might occur after liability was found, depending on whether the trial was bifurcated. But, now is way too early to give such information. Shutting down the website will likely satisfy the one who notified you, unless they are working on a contingent fee, in which case you definitely do not want to give them anything you are not required to give. You need to hire a copyright infringement defense attorney or an internet attorney right away and do not respond at all to the notice, let your copyright attorney do that.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.