I need to:
Get my products from my market (filter the products by sellerId/merchantId, hipotetically) on Amazon by API.
Render the products in my webpage outside Amazon.
Use Amazon FPS to allow user to purchase my product.
Point #3 is quite clear for me. But #1 which seems the simplest I really don't know how to do. I also tried Amazon MarketPlace Webservice and Amazon Product Advertising API but without success.
Until recently, you could use the Product Advertising API to look up products from a given merchant. Now, you need to use the Amazon Marketplace Web Service and programmatically request a report for all your listings (using the "GetReportRequestList" operation with the report type "_GET_FLAT_FILE_OPEN_LISTINGS_DATA_"). See the Report API Reference (in PDF) for details.
Let me know if you need additional information.