6. Is it possible to store a database of cargo items directly in the app?

Yes, under the tab Cargo Items you can easily add, import, and maintain a database of cargo items:

In EasyCargo, these items can be simply added by entering part of the cargo item’s name in the editor, and all the item’s properties will be automatically prefilled from the database:

Cargo Items database API is also already available (see the question Is integration via API possible?).