NECPA - do not attend this meeting without getting a POA and meeting with your client beforehand. If he is not willing to do this then the client needs to leave you completely out of the process - and you need to stay out of it. You can provide the client copies of what you can but that is it. Before you ever sit down with the IRS you need to know what the client has told them and what issues are being questioned. The agent should, once you have the POA, meet with you and be willing to discuss all the issues discussed and then give you a document request to answer their questions.
And this looks like a client that needs to "leave" !!