> Identity of the customer making the purchase;
> Identity of goods sold; and
> Quantity of goods sold.
You do not have to provide any of that, they have no legal right to the information and it would be a violation of your Amazon Participation Agreement to disclose your buyers’ names
>Source of goods
This is what they are after
You need to prove that your items are genuine and that you are an authorized dealer. The way to do this is to send them copies of your brand-authorized distributor wholesale invoices for these line items.
Assuming that you are not in fact an authorized dealer, that your did not purchase from an authorized wholesaler, and you did list as New, then you need to delete all items from this brand, tell them you have deleted them, and promise never to sell the brand again. You can provide them with your Retail receipts, assuming you bought from a retailer, to convince them that these were not counterfeit product.
If you have not in fact sold any units, tell them this. But do not admit to selling X quantity.
You are basically grovelling and asking for them to drop the matter before they escalate it to Amazon as a Possibly Counterfeit claim which you will have a very hard time discharging.