Aggregating ebay data, storing sales data, account deletion notification endpoint

Hello developers and ebay dev team. I am in the middle of developing an application and would like to aggregate historical sales data of a certain type of collectible so that users on my platform can see the change in their "collectible portfolio" overtime. I am planning to do this via the FindingService endpoint.

I also plan on providing an ebay links to collectibles to drive traffic to ebay's platform. It would be ideal if I could store sales data for items in my own database, perform aggregations and then serve to users rather than making API calls and aggregating on demand but I heard that you need written permission to persist ebay data for more than 24 hours???

I need access to the production keysets so that I can test my application with real world data before I launch it. Do I need to set up user account deletion notification endpoint if I'm storing sold item data rather than personal data about users?

Thanks in advance for the advice.